feat: Rely on highligher.sile for syntax highlighting in code blocks

Author: Omikhleia

README.md

@@ -147,7 +147,7 @@ This is but an overview. For more details, please refer to the provided example
   - Definition lists
 - Horizontal dividers / thematic breaks (with provision for asterisms, dinkuses, pendants...)
 - Tables (and table captions)
-- Code blocks (with attributes)
+- Code blocks (with attributes, and syntax highlighting when supported)
 - Line blocks (with enhanced provision for poetry)
 - Raw inlines and raw blocks (escaping to SILE, in SIL language or Lua scripting)
 - Raw inline HTML convenience subset in Markdown

examples/markdown-sile-overview.dot

@@ -18,9 +18,9 @@ digraph G {
   }
 
   sile [shape=doublecircle, color="#e8ccd7 ", style=filled, label="SILE"];
-  
+
   pandoc [shape=doublecircle, color="#d0d0d0", style=filled, label="Pandoc", fontsize=12];
-  
+
   ast [shape=note, label="Pandoc\nAST", color="#c0c0c0", fontsize=12];
 
   doc -> sile [label="native path", fontsize=11]

examples/markdown-sile-schema.dot

@@ -1,12 +1,22 @@
 digraph omikhleia {
-	rankdir=RL;
+  rankdir=RL;
+  compound=true;
+  edge [
+    arrowhead="vee"
+  ];
 
   subgraph cluster_couyards {
     label = "couyards.sile";
 
     couyards [shape=component,style=filled,fillcolor=aliceblue]
   }
 
+  subgraph cluster_piecharts {
+    label = "piecharts.sile";
+
+    piecharts [shape=component,style=filled,fillcolor=aliceblue]
+  }
+
   subgraph cluster_ptable {
     label = "ptable.sile";
 
@@ -18,9 +28,9 @@ digraph omikhleia {
 
     embedders [shape=component,style=filled,fillcolor=aliceblue]
     dot [style=filled,fillcolor=aliceblue]
-      
+
     embedders -> dot
-  }  
+  }
 
   subgraph cluster_textsubsuper {
     label = "textsubsuper.sile";
@@ -34,18 +44,26 @@ digraph omikhleia {
     smartquotes [shape=component,style=filled,fillcolor=aliceblue]
 
   }
-  
+
   subgraph cluster_labelrefs {
     label = "labelrefs.sile";
 
     labelrefs [shape=component,style=filled,fillcolor=aliceblue]
   }
 
+  subgraph cluster_highlighter {
+    label = "highlighter.sile";
+
+    highlighter [shape=component,style=filled,fillcolor=aliceblue]
+  }
+
   subgraph cluster_resilient {
     label = "resilient.sile";
 
     book [shape=component,style=filled,fillcolor=aliceblue,label="resilient.book"]
     poetry [shape=component,style=filled,fillcolor=aliceblue,label="resilient.poetry"]
+    defn [shape=component,style=filled,fillcolor=aliceblue,label="resilient.defn"]
+    epigraph [shape=component,style=filled,fillcolor=aliceblue,label="resilient.epigraph"]
   }
 
   subgraph cluster_markdown {
@@ -66,13 +84,14 @@ digraph omikhleia {
     mrkcmd -> ptable
     mrkcmd -> smartquotes
     mrkcmd -> textsubsuper
-    mrkcmd -> poetry [style=dashed]
-    mrkcmd -> book [style=dashed]
+    mrkcmd -> highlighter
     mrkcmd -> couyards [style=dashed]
+    mrkcmd -> piecharts [style=dashed]
   }
-  
+
   mybook [shape = circle, label="Markdown\nfor\nSILE", fontsize="25"]
   mybook -> markdown
   mybook -> pandocast
   mybook -> djot
+  mybook -> book [style=dashed, lhead=cluster_resilient]
 }

examples/sile-and-djot.dj

@@ -346,8 +346,6 @@ Files in Graphviz DOT graph language (`.dot`) are supported and rendered as imag
 
 ![The *markdown.sile* ecosystem (simplified).](./markdown-sile-schema.dot){width="90%"}
 
-This image is obtained with the following syntax.
-
 {custom-style=CodeBlock}
 :::
 ```
@@ -621,7 +619,7 @@ Here is an example illustrating the use of these attributes:
 
 Other attributes are passed through to the underlying heading implementation, which might do something with them.[^djot-heading-level-mapping]
 
-[^djot-heading-level-mapping]: The converter assumes it can map heading levels to SILE commands `part`, `chapter`, `section`, `subsection`, `subsubsection`.
+[^djot-heading-level-mapping]: The converter assumes it can map heading levels to commands `part`, `chapter`, `section`, `subsection`, `subsubsection`.
 It uses a very basic fallback if these are not found (or if the sectioning level gets past that point).
 Also note that parts are supported by the *resilient* book class as a level 0 heading, and are therefore only available when header shifting is applied (see §[](#djot-configuration)).
 
@@ -931,7 +929,7 @@ In most cases, the content is rendered as verbatim text, with some exceptions de
 
 #### Lua code blocks
 
-Code blocks marked as being in the Lua language are rendered as verbatim text, with syntax highlighting.
+Code blocks are rendered as verbatim text, with syntax highlighting when possible.
 For instance, the following code block...
 
 {custom-style=CodeBlock}
@@ -962,12 +960,12 @@ end
 ^ An example of a syntax-highlighted Lua code snippet.
 
 
-This is a very naive approach to syntax-highlighting, until the converter possibly supports a more general solution.
+Syntax-highlighting is applied to languages recognized by Scintillua.
 
 #### Rendered code blocks
 
 If the converter knows how to render the content of a code block, it does so by default.
-The `render` attribute can be set to `false` to prevent this behavior, and enforce the content to be rendered as raw verbatim text.
+The `render` attribute can be set to `false` to prevent this behavior, and enforce the content to be rendered as raw verbatim text (possibly with syntax highlighting).
 
 : Mardown and Djot code blocks