Extract HTML support into an extension (#10130)

This PR extracts HTML support into an extension and removes the built-in
HTML support from Zed.

Release Notes:

- Removed built-in support for HTML, in favor of making it available as
an extension. The HTML extension will be suggested for download when you
open a `.html`, `.htm`, or `.shtml` file.

extensions/html/languages/html/brackets.scm

@@ -0,0 +1,2 @@
+("<" @open ">" @close)
+("\"" @open "\"" @close)

extensions/html/languages/html/config.toml

@@ -0,0 +1,15 @@
+name = "HTML"
+grammar = "html"
+path_suffixes = ["html", "htm", "shtml"]
+autoclose_before = ">})"
+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 = ["comment", "string"] },
+    { start = "<", end = ">", close = true, newline = true, not_in = ["comment", "string"] },
+    { start = "!--", end = " --", close = true, newline = false, not_in = ["comment", "string"] },
+]
+word_characters = ["-"]
+prettier_parser_name = "html"

extensions/html/languages/html/highlights.scm

@@ -0,0 +1,16 @@
+(tag_name) @keyword
+(erroneous_end_tag_name) @keyword
+(doctype) @constant
+(attribute_name) @property
+(attribute_value) @string
+(comment) @comment
+
+"=" @operator
+
+[
+  "<"
+  ">"
+  "<!"
+  "</"
+  "/>"
+] @punctuation.bracket

extensions/html/languages/html/indents.scm

@@ -0,0 +1,6 @@
+(start_tag ">" @end) @indent
+(self_closing_tag "/>" @end) @indent
+
+(element
+  (start_tag) @start
+  (end_tag)? @end) @indent

extensions/html/languages/html/injections.scm

@@ -0,0 +1,7 @@
+(script_element
+  (raw_text) @content
+  (#set! "language" "javascript"))
+
+(style_element
+  (raw_text) @content
+  (#set! "language" "css"))

extensions/html/languages/html/overrides.scm

@@ -0,0 +1,2 @@
+(comment) @comment
+(quoted_attribute_value) @string