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/p/postscript.go

@@ -0,0 +1,46 @@
+package p
+
+import (
+	. "github.com/alecthomas/chroma" // nolint
+	"github.com/alecthomas/chroma/lexers/internal"
+)
+
+// Postscript lexer.
+var Postscript = internal.Register(MustNewLexer(
+	&Config{
+		Name:      "PostScript",
+		Aliases:   []string{"postscript", "postscr"},
+		Filenames: []string{"*.ps", "*.eps"},
+		MimeTypes: []string{"application/postscript"},
+	},
+	Rules{
+		"root": {
+			{`^%!.+\n`, CommentPreproc, nil},
+			{`%%.*\n`, CommentSpecial, nil},
+			{`(^%.*\n){2,}`, CommentMultiline, nil},
+			{`%.*\n`, CommentSingle, nil},
+			{`\(`, LiteralString, Push("stringliteral")},
+			{`[{}<>\[\]]`, Punctuation, nil},
+			{`<[0-9A-Fa-f]+>(?=[()<>\[\]{}/%\s])`, LiteralNumberHex, nil},
+			{`[0-9]+\#(\-|\+)?([0-9]+\.?|[0-9]*\.[0-9]+|[0-9]+\.[0-9]*)((e|E)[0-9]+)?(?=[()<>\[\]{}/%\s])`, LiteralNumberOct, nil},
+			{`(\-|\+)?([0-9]+\.?|[0-9]*\.[0-9]+|[0-9]+\.[0-9]*)((e|E)[0-9]+)?(?=[()<>\[\]{}/%\s])`, LiteralNumberFloat, nil},
+			{`(\-|\+)?[0-9]+(?=[()<>\[\]{}/%\s])`, LiteralNumberInteger, nil},
+			{`\/[^()<>\[\]{}/%\s]+(?=[()<>\[\]{}/%\s])`, NameVariable, nil},
+			{`[^()<>\[\]{}/%\s]+(?=[()<>\[\]{}/%\s])`, NameFunction, nil},
+			{`(false|true)(?=[()<>\[\]{}/%\s])`, KeywordConstant, nil},
+			{`(eq|ne|g[et]|l[et]|and|or|not|if(?:else)?|for(?:all)?)(?=[()<>\[\]{}/%\s])`, KeywordReserved, nil},
+			{Words(``, `(?=[()<>\[\]{}/%\s])`, `abs`, `add`, `aload`, `arc`, `arcn`, `array`, `atan`, `begin`, `bind`, `ceiling`, `charpath`, `clip`, `closepath`, `concat`, `concatmatrix`, `copy`, `cos`, `currentlinewidth`, `currentmatrix`, `currentpoint`, `curveto`, `cvi`, `cvs`, `def`, `defaultmatrix`, `dict`, `dictstackoverflow`, `div`, `dtransform`, `dup`, `end`, `exch`, `exec`, `exit`, `exp`, `fill`, `findfont`, `floor`, `get`, `getinterval`, `grestore`, `gsave`, `gt`, `identmatrix`, `idiv`, `idtransform`, `index`, `invertmatrix`, `itransform`, `length`, `lineto`, `ln`, `load`, `log`, `loop`, `matrix`, `mod`, `moveto`, `mul`, `neg`, `newpath`, `pathforall`, `pathbbox`, `pop`, `print`, `pstack`, `put`, `quit`, `rand`, `rangecheck`, `rcurveto`, `repeat`, `restore`, `rlineto`, `rmoveto`, `roll`, `rotate`, `round`, `run`, `save`, `scale`, `scalefont`, `setdash`, `setfont`, `setgray`, `setlinecap`, `setlinejoin`, `setlinewidth`, `setmatrix`, `setrgbcolor`, `shfill`, `show`, `showpage`, `sin`, `sqrt`, `stack`, `stringwidth`, `stroke`, `strokepath`, `sub`, `syntaxerror`, `transform`, `translate`, `truncate`, `typecheck`, `undefined`, `undefinedfilename`, `undefinedresult`), NameBuiltin, nil},
+			{`\s+`, Text, nil},
+		},
+		"stringliteral": {
+			{`[^()\\]+`, LiteralString, nil},
+			{`\\`, LiteralStringEscape, Push("escape")},
+			{`\(`, LiteralString, Push()},
+			{`\)`, LiteralString, Pop(1)},
+		},
+		"escape": {
+			{`[0-8]{3}|n|r|t|b|f|\\|\(|\)`, LiteralStringEscape, Pop(1)},
+			Default(Pop(1)),
+		},
+	},
+))