Adds the help dialog and written documentation. The actual code changes here are pretty minimal and most of the PR is the written documentation for each dialog. This uses Qt's help system which requires Qt's QSLite SQL driver which this adds to the build workflows. I'm inexperienced with CMAKE but I've got this working such that building QtFRED will compile the help file and copy it next to the exe.

The help system I've setup here is one where SCP will take ownership of keeping the dialog documentation up to date. Any time features are added/changed/removed from a dialog, the associated help html file should also be updated. Additionally, the help dialog will search in data/freddocs for loose html files and add them to the Tutorials tab. This is intended to provide mods like FOTG a way to inject mod-specific documentation directly into the help window. These html files will obey the dark/light theme, be searchable, and can link directly internal dialog documentation. An example html file has been included with this PR.

An overwhelming majority of the lines/files changed here is the actual documentation files. Some of them, like sexps, are placeholder. I've asked naomi to help write more complete versions because she is an experienced tutor.