languages: Separate control flow keywords for JS/TS/TSX (#39801)

Related to #9461, inspired by #39683

`await` and `yield` both seem somewhat debatable on whether they should
be considered the be control flow keywords.

For now I went with:
- `await`: no – The control flow effect of `await` is at a level does
not seem relevant for syntax highlighting.
- `yield`: yes – `yield` directly affects the output of a generator, and
is also included for consistency with Rust (#39683).
 
 Happy to change these either direction.

<img width="1151" height="730" alt="SCR-20251008-izus"
src="https://github.com/user-attachments/assets/533ea670-863a-4c5c-aaa5-4a9bfa0bf0dd"
/>

--- 

Release Notes:

- Improved granularity of keyword highlighting for JS/TS/TSX: Themes can
now specify `keyword.control` for control flow keywords like `if`,
`else`, `return`, etc.

crates/languages/src/javascript/highlights.scm

@@ -171,47 +171,52 @@
   "as"
   "async"
   "await"
-  "break"
-  "case"
-  "catch"
   "class"
   "const"
-  "continue"
   "debugger"
   "default"
   "delete"
-  "do"
-  "else"
   "export"
   "extends"
-  "finally"
-  "for"
   "from"
   "function"
   "get"
-  "if"
   "import"
   "in"
   "instanceof"
   "let"
   "new"
   "of"
-  "return"
   "set"
   "static"
-  "switch"
   "target"
-  "throw"
-  "try"
   "typeof"
   "using"
   "var"
   "void"
-  "while"
   "with"
-  "yield"
 ] @keyword
 
+[
+  "break"
+  "case"
+  "catch"
+  "continue"
+  "do"
+  "else"
+  "finally"
+  "for"
+  "if"
+  "return"
+  "switch"
+  "throw"
+  "try"
+  "while"
+  "yield"
+] @keyword.control
+
+(switch_default "default" @keyword.control)
+
 (template_substitution
   "${" @punctuation.special
   "}" @punctuation.special) @embedded

crates/languages/src/tsx/highlights.scm

@@ -171,25 +171,16 @@
   "as"
   "async"
   "await"
-  "break"
-  "case"
-  "catch"
   "class"
   "const"
-  "continue"
   "debugger"
   "default"
   "delete"
-  "do"
-  "else"
   "export"
   "extends"
-  "finally"
-  "for"
   "from"
   "function"
   "get"
-  "if"
   "import"
   "in"
   "instanceof"
@@ -197,23 +188,37 @@
   "let"
   "new"
   "of"
-  "return"
   "satisfies"
   "set"
   "static"
-  "switch"
   "target"
-  "throw"
-  "try"
   "typeof"
   "using"
   "var"
   "void"
-  "while"
   "with"
-  "yield"
 ] @keyword
 
+[
+  "break"
+  "case"
+  "catch"
+  "continue"
+  "do"
+  "else"
+  "finally"
+  "for"
+  "if"
+  "return"
+  "switch"
+  "throw"
+  "try"
+  "while"
+  "yield"
+] @keyword.control
+
+(switch_default "default" @keyword.control)
+
 (template_substitution
   "${" @punctuation.special
   "}" @punctuation.special) @embedded

crates/languages/src/typescript/highlights.scm

@@ -218,27 +218,18 @@
   "as"
   "async"
   "await"
-  "break"
-  "case"
-  "catch"
   "class"
   "const"
-  "continue"
   "debugger"
   "declare"
   "default"
   "delete"
-  "do"
-  "else"
   "enum"
   "export"
   "extends"
-  "finally"
-  "for"
   "from"
   "function"
   "get"
-  "if"
   "implements"
   "import"
   "in"
@@ -257,20 +248,34 @@
   "protected"
   "public"
   "readonly"
-  "return"
   "satisfies"
   "set"
   "static"
-  "switch"
   "target"
-  "throw"
-  "try"
   "type"
   "typeof"
   "using"
   "var"
   "void"
-  "while"
   "with"
-  "yield"
 ] @keyword
+
+[
+  "break"
+  "case"
+  "catch"
+  "continue"
+  "do"
+  "else"
+  "finally"
+  "for"
+  "if"
+  "return"
+  "switch"
+  "throw"
+  "try"
+  "while"
+  "yield"
+] @keyword.control
+
+(switch_default "default" @keyword.control)