Extract Elm language into an extension (#10432)

Release Notes:

- Extracted Elm language support into an extension

Co-authored-by: Marshall <marshall@zed.dev>

extensions/elm/languages/elm/config.toml

@@ -0,0 +1,13 @@
+name = "Elm"
+grammar = "elm"
+path_suffixes = ["elm"]
+line_comments = ["-- "]
+block_comment = ["{- ", " -}"]
+brackets = [
+    { start = "{", end = "}", close = true, newline = true },
+    { start = "[", end = "]", close = true, newline = true },
+    { start = "(", end = ")", close = true, newline = true },
+    { start = "\"", end = "\"", close = true, newline = false, not_in = ["string"] },
+    { start = "'", end = "'", close = true, newline = false, not_in = ["string", "comment"] },
+]
+tab_size = 2

extensions/elm/languages/elm/highlights.scm

@@ -0,0 +1,72 @@
+[
+    "if"
+    "then"
+    "else"
+    "let"
+    "in"
+    (case)
+    (of)
+    (backslash)
+    (as)
+    (port)
+    (exposing)
+    (alias)
+    (import)
+    (module)
+    (type)
+    (arrow)
+ ] @keyword
+
+[
+    (eq)
+    (operator_identifier)
+    (colon)
+] @operator
+
+(type_annotation(lower_case_identifier) @function)
+(port_annotation(lower_case_identifier) @function)
+(function_declaration_left(lower_case_identifier) @function.definition)
+
+(function_call_expr
+    target: (value_expr
+        name: (value_qid (lower_case_identifier) @function)))
+
+(exposed_value(lower_case_identifier) @function)
+(exposed_type(upper_case_identifier) @type)
+
+(field_access_expr(value_expr(value_qid)) @identifier)
+(lower_pattern) @variable
+(record_base_identifier) @identifier
+
+[
+    "("
+    ")"
+] @punctuation.bracket
+
+[
+    "|"
+    ","
+] @punctuation.delimiter
+
+(number_constant_expr) @constant
+
+(type_declaration(upper_case_identifier) @type)
+(type_ref) @type
+(type_alias_declaration name: (upper_case_identifier) @type)
+
+(value_expr(upper_case_qid(upper_case_identifier)) @type)
+
+[
+    (line_comment)
+    (block_comment)
+] @comment
+
+(string_escape) @string.escape
+
+[
+    (open_quote)
+    (close_quote)
+    (regular_string_part)
+    (open_char)
+    (close_char)
+] @string

extensions/elm/languages/elm/injections.scm

@@ -0,0 +1,2 @@
+((glsl_content) @content
+ (#set! "language" "glsl"))

extensions/elm/languages/elm/outline.scm

@@ -0,0 +1,22 @@
+(type_declaration
+    (type) @context
+    (upper_case_identifier) @name) @item
+
+(type_alias_declaration
+    (type) @context
+    (alias) @context
+    name: (upper_case_identifier) @name) @item
+
+(type_alias_declaration
+    typeExpression:
+        (type_expression
+            part: (record_type
+                (field_type
+                    name: (lower_case_identifier) @name) @item)))
+
+(union_variant
+    name: (upper_case_identifier) @name) @item
+
+(value_declaration
+    functionDeclarationLeft:
+        (function_declaration_left(lower_case_identifier) @name)) @item