Reflect Perl6 to Raku rename

+ [Raku](https://raku.org/) language has been renamed since October 2019
+ The command to execute Raku scripts is `raku` command
+ Perl 6 FE extension used `perl.coffee` is renamed to `Perl 6` Raku/atom-language@7068090

So this commit

Author: sumanstats

README.md

@@ -78,8 +78,8 @@ Currently supported grammars are:
 | [Oz]                                | Yes        | Yes             | [language-oz]                 | `ozc`                     |                                                                                                                                                                                                                                                                 |
 | [Pandoc] Markdown                   | Yes        |                 | [language-pfm]                | [`panzer`]                |                                                                                                                                                                                                                                                                 |
 | [Pascal]                            | Yes        | Yes             | [language-pascal]             | `fpc`                     |                                                                                                                                                                                                                                                                 |
-| Perl                                | Yes        | Yes             |                               |                           |                                                                                                                                                                                                                                                                 |
-| [Perl 6]                            | Yes        | Yes             |                               | `perl6`                   |                                                                                                                                                                                                                                                                 |
+| [Perl]                                | Yes        | Yes             |                               |                           |                                                                                                                                                                                                                                                                 |
+| [Raku]                            | Yes        | Yes             |                               | `raku` or `perl6`                   |                                                                                                                                                                                                                                                                 |
 | PHP                                 | Yes        | Yes             |                               |                           |                                                                                                                                                                                                                                                                 |
 | [PostgreSQL]                        | Yes        | Yes             | [language-pgsql]              | [`psql`]                  | Connects as user `PGUSER` to database `PGDATABASE`. Both default to your operating system's `USERNAME`, but can be set in the process environment or in Atom's [`init` file]: `process.env.PGUSER = {user name}` and `process.env.PGDATABASE = {database name}` |
 | [POV-Ray]                           | Yes        |                 | [atom-language-povray]        | `povengine`/`povray`      |                                                                                                                                                                                                                                                                 |
@@ -264,8 +264,9 @@ Currently supported grammars are:
 [octave]:                       https://gnu.org/software/octave
 [oz]:                           https://mozart.github.io
 [pandoc]:                       https://pandoc.org
-[perl 6]:                       https://perl6.org
+[Raku]:                         https://raku.org
 [pascal]:                       https://freepascal.org
+[Perl]:                         https://www.perl.org/              
 [PostgreSQL]:                   https://postgresql.org
 [POV-Ray]:                      http://www.povray.org/
 [powershell]:                   https://docs.microsoft.com/powershell

lib/grammars/perl.coffee

@@ -12,13 +12,13 @@ exports.Perl =
     command: 'perl'
     args: ({filepath}) -> [filepath]
 
-exports['Perl 6'] =
+exports['Raku'] =
   'Selection Based':
-    command: 'perl6'
+    command: 'raku'
     args: (context) -> ['-e', context.getCode()]
 
   'File Based':
-    command: 'perl6'
+    command: 'raku'
     args: ({filepath}) -> [filepath]
 
-exports['Perl 6 FE'] = exports['Perl 6']
+exports['Raku/Perl 6'] = exports['Raku']