Add syntax highlighting for if-else (#4090)

* Add syntax highlighting for if-else

* A snapshot a day keeps the bugs away! 📷🐛 (OS: windows-latest)

* Confirm

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Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

src/editor/plugins/lsp/kcl/highlight.ts

@@ -2,6 +2,7 @@ import { styleTags, tags as t } from '@lezer/highlight'
 
 export const kclHighlight = styleTags({
   'fn var let const': t.definitionKeyword,
+  'if else': t.controlKeyword,
   return: t.controlKeyword,
   'true false': t.bool,
   nil: t.null,

src/editor/plugins/lsp/kcl/kcl.grammar

@@ -40,6 +40,7 @@ expression[@isGroup=Expression] {
   } |
   UnaryExpression { UnaryOp expression } |
   ParenthesizedExpression { "(" expression ")" } |
+  IfExpression { kw<"if"> expression Body kw<"else"> Body } |
   CallExpression { expression !call ArgumentList } |
   ArrayExpression { "[" commaSep<expression | IntegerRange { expression !range ".." expression }> "]" } |
   ObjectExpression { "{" commaSep<ObjectProperty> "}" } |