Centralize developer documentation. (#26485)

* Documentation.

* Documentation.

* Testing reqs update

* Post feature-freeze code of conduct updates

* spell checking

* Style Guidelines

* wrap

* link up, bring headers up one level

* wrap

* fix old link

* support github admonition syntax for mkdocs

* link rules, rename to guard clauses

* ffffucking vscode

---------

Co-authored-by: Burzah <116982774+Burzah@users.noreply.github.com>

docs/javascripts/highlight-dm.js

@@ -0,0 +1,113 @@
+// This is a grammar for highlight.js used by mdbook.
+//
+// - Guide on writing highlighters: https://highlightjs.readthedocs.io/en/latest/language-guide.html
+// - possible values for `scope`/`className`: https://highlightjs.readthedocs.io/en/latest/css-classes-reference.html
+
+/*
+Language: Dream Maker
+Author: Pieter-Jan Briers <pieterjan.briers@gmail.com>
+Various bits taken from Javascript, Rust and C++'s file.
+Description: Dream Maker language used by the BYOND game engine.
+Category: common
+*/
+
+var BLOCK_COMMENT = hljs.COMMENT('/\\*', '\\*/', {contains: ['self']});
+var KEYWORDS =
+  'var proc verb global tmp static const set as ' +
+  'new del ' +
+  'sleep spawn break continue do else for in step goto if return switch while try catch throw';
+var BUILTINS =
+  'usr src world args ' +
+  'list datum area turf obj mob atom movable client database exception ' +
+  'icon image matrix mutable_appearance savefile sound regex operator';
+var LITERAL = 'null';
+var SUBST = {
+  className: 'subst',
+  begin: '\\[', end: '\\]',
+  keywords: {
+	built_in: BUILTINS,
+	literal: LITERAL
+  },
+  contains: []  // defined later
+};
+var STRING = {
+  className: 'string',
+  begin: '"', end: '"',
+  contains: [
+	hljs.BACKSLASH_ESCAPE,
+	SUBST
+  ]
+};
+var STRING_MULTILINE = {
+  className: 'string',
+  begin: '\\{"', end: '"\\}',
+  contains: [
+	hljs.BACKSLASH_ESCAPE,
+	SUBST
+  ]
+};
+var FILE_STRING = {
+  className: 'string',
+  begin: "'", end: "'"
+};
+var NUMBER = {
+  className: 'number',
+  variants: [
+	{ begin: '1\\.\\#IND' },
+	{ begin: '1\\.\\#INF' },
+	{ begin: hljs.C_NUMBER_RE },
+  ],
+  relevance: 0
+};
+var CONSTANT = {
+  className: 'literal',
+  begin: /\b[A-Z_][A-Z_0-9]*\b/
+};
+var PREPROCESSOR = {
+  className: 'meta',
+  begin: /#\s*[a-z]+\b/, end: /$/,
+  keywords: {
+	'meta-keyword':
+	  'if else elif endif define undef warn error ' +
+	  'ifdef ifndef include'
+  },
+  contains: [
+	{
+	  begin: /\\\n/, relevance: 0
+	},
+	STRING,
+	FILE_STRING,
+	NUMBER,
+	CONSTANT,
+	hljs.C_LINE_COMMENT_MODE,
+	BLOCK_COMMENT,
+  ]
+};
+SUBST.contains = [
+  STRING,
+  FILE_STRING,
+  NUMBER,
+  CONSTANT
+];
+
+hljs.registerLanguage('dm', (hljs) => ({
+	  aliases: ['byond', 'dreammaker'],
+	  keywords: {
+		keyword: KEYWORDS,
+		literal: LITERAL,
+		built_in: BUILTINS
+	  },
+	  contains: [
+		hljs.C_LINE_COMMENT_MODE,
+		BLOCK_COMMENT,
+		PREPROCESSOR,
+		STRING,
+		FILE_STRING,
+		STRING_MULTILINE,
+		NUMBER,
+		CONSTANT
+	  ]
+  }));
+
+hljs.initHighlightingOnLoad();
+

docs/javascripts/init.js

@@ -0,0 +1 @@
+hljs.highlightAll();