feat(diff/syntax-highlight): add Elixir language support

Add community provided Elixir language parser to the utils/diffParsing 
module, allowing syntax highlighting of `*.ex` and `*.exs` files in 
diffs.

Changes:

- Install `codemirror-lang-elixir` package as a dependency.
- Add Elixir file extension detection in `parserFromExtension`.

Author: jimeh

packages/ui/package.json

@@ -65,6 +65,7 @@
 		"@types/postcss-pxtorem": "^6.1.0",
 		"@vitest/browser": "catalog:",
 		"autoprefixer": "^10.4.21",
+		"codemirror-lang-elixir": "^4.0.0",
 		"codemirror-lang-hcl": "^0.1.0",
 		"cpy-cli": "^5.0.0",
 		"cssnano": "^7.1.0",

packages/ui/src/lib/utils/diffParsing.ts

@@ -29,6 +29,7 @@ import { toml } from '@codemirror/legacy-modes/mode/toml';
 import { NodeType, Tree, Parser } from '@lezer/common';
 import { tags, highlightTree } from '@lezer/highlight';
 import { nix } from '@replit/codemirror-lang-nix';
+import { elixir } from 'codemirror-lang-elixir';
 import { hcl } from 'codemirror-lang-hcl';
 import diff_match_patch from 'diff-match-patch';
 import type { BrandedId } from '$lib/utils/branding';
@@ -277,6 +278,10 @@ export function parserFromExtension(extension: string): Parser | undefined {
 		case 'h++':
 			return cpp().language.parser;
 
+		case 'ex':
+		case 'exs':
+			return elixir().language.parser;
+
 		case 'go':
 			return go().language.parser;