Server-side syntax highlighting for all code (#12047)

* Server-side syntax hilighting for all code

This PR does a few things:

* Remove all traces of highlight.js
* Use chroma library to provide fast syntax hilighting directly on the server
* Provide syntax hilighting for diffs
* Re-style both unified and split diffs views
* Add custom syntax hilighting styling for both regular and arc-green

Fixes #7729
Fixes #10157
Fixes #11825
Fixes #7728
Fixes #3872
Fixes #3682

And perhaps gets closer to #9553

* fix line marker

* fix repo search

* Fix single line select

* properly load settings

* npm uninstall highlight.js

* review suggestion

* code review

* forgot to call function

* fix test

* Apply suggestions from code review

suggestions from @silverwind thanks

Co-authored-by: silverwind <me@silverwind.io>

* code review

* copy/paste error

* Use const for highlight size limit

* Update web_src/less/_repository.less

Co-authored-by: Lauris BH <lauris@nix.lv>

* update size limit to 1MB and other styling tweaks

* fix highlighting for certain diff sections

* fix test

* add worker back as suggested

Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: Lauris BH <lauris@nix.lv>

vendor/github.com/alecthomas/chroma/lexers/b/blitz.go

@@ -0,0 +1,48 @@
+package b
+
+import (
+	. "github.com/alecthomas/chroma" // nolint
+	"github.com/alecthomas/chroma/lexers/internal"
+)
+
+// Blitzbasic lexer.
+var Blitzbasic = internal.Register(MustNewLexer(
+	&Config{
+		Name:            "BlitzBasic",
+		Aliases:         []string{"blitzbasic", "b3d", "bplus"},
+		Filenames:       []string{"*.bb", "*.decls"},
+		MimeTypes:       []string{"text/x-bb"},
+		CaseInsensitive: true,
+	},
+	Rules{
+		"root": {
+			{`[ \t]+`, Text, nil},
+			{`;.*?\n`, CommentSingle, nil},
+			{`"`, LiteralStringDouble, Push("string")},
+			{`[0-9]+\.[0-9]*(?!\.)`, LiteralNumberFloat, nil},
+			{`\.[0-9]+(?!\.)`, LiteralNumberFloat, nil},
+			{`[0-9]+`, LiteralNumberInteger, nil},
+			{`\$[0-9a-f]+`, LiteralNumberHex, nil},
+			{`\%[10]+`, LiteralNumberBin, nil},
+			{Words(`\b`, `\b`, `Shl`, `Shr`, `Sar`, `Mod`, `Or`, `And`, `Not`, `Abs`, `Sgn`, `Handle`, `Int`, `Float`, `Str`, `First`, `Last`, `Before`, `After`), Operator, nil},
+			{`([+\-*/~=<>^])`, Operator, nil},
+			{`[(),:\[\]\\]`, Punctuation, nil},
+			{`\.([ \t]*)([a-z]\w*)`, NameLabel, nil},
+			{`\b(New)\b([ \t]+)([a-z]\w*)`, ByGroups(KeywordReserved, Text, NameClass), nil},
+			{`\b(Gosub|Goto)\b([ \t]+)([a-z]\w*)`, ByGroups(KeywordReserved, Text, NameLabel), nil},
+			{`\b(Object)\b([ \t]*)([.])([ \t]*)([a-z]\w*)\b`, ByGroups(Operator, Text, Punctuation, Text, NameClass), nil},
+			{`\b([a-z]\w*)(?:([ \t]*)(@{1,2}|[#$%])|([ \t]*)([.])([ \t]*)(?:([a-z]\w*)))?\b([ \t]*)(\()`, ByGroups(NameFunction, Text, KeywordType, Text, Punctuation, Text, NameClass, Text, Punctuation), nil},
+			{`\b(Function)\b([ \t]+)([a-z]\w*)(?:([ \t]*)(@{1,2}|[#$%])|([ \t]*)([.])([ \t]*)(?:([a-z]\w*)))?`, ByGroups(KeywordReserved, Text, NameFunction, Text, KeywordType, Text, Punctuation, Text, NameClass), nil},
+			{`\b(Type)([ \t]+)([a-z]\w*)`, ByGroups(KeywordReserved, Text, NameClass), nil},
+			{`\b(Pi|True|False|Null)\b`, KeywordConstant, nil},
+			{`\b(Local|Global|Const|Field|Dim)\b`, KeywordDeclaration, nil},
+			{Words(`\b`, `\b`, `End`, `Return`, `Exit`, `Chr`, `Len`, `Asc`, `New`, `Delete`, `Insert`, `Include`, `Function`, `Type`, `If`, `Then`, `Else`, `ElseIf`, `EndIf`, `For`, `To`, `Next`, `Step`, `Each`, `While`, `Wend`, `Repeat`, `Until`, `Forever`, `Select`, `Case`, `Default`, `Goto`, `Gosub`, `Data`, `Read`, `Restore`), KeywordReserved, nil},
+			{`([a-z]\w*)(?:([ \t]*)(@{1,2}|[#$%])|([ \t]*)([.])([ \t]*)(?:([a-z]\w*)))?`, ByGroups(NameVariable, Text, KeywordType, Text, Punctuation, Text, NameClass), nil},
+		},
+		"string": {
+			{`""`, LiteralStringDouble, nil},
+			{`"C?`, LiteralStringDouble, Pop(1)},
+			{`[^"]+`, LiteralStringDouble, nil},
+		},
+	},
+))