Extract Astro support into an extension (#9835)

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

Release Notes:

- Removed built-in support for Astro, in favor of making it available as
an extension. The Astro extension will be suggested for download when
you open a `.astro` file.

extensions/astro/languages/astro/brackets.scm

@@ -0,0 +1,3 @@
+("{" @open "}" @close)
+("<" @open ">" @close)
+("\"" @open "\"" @close)

extensions/astro/languages/astro/config.toml

@@ -0,0 +1,23 @@
+name = "Astro"
+grammar = "astro"
+path_suffixes = ["astro"]
+block_comment = ["<!-- ", " -->"]
+autoclose_before = ";:.,=}])>"
+brackets = [
+    { start = "{", end = "}", close = true, newline = true },
+    { start = "[", end = "]", close = true, newline = true },
+    { start = "(", end = ")", close = true, newline = true },
+    { start = "<", end = ">", close = false, newline = true, not_in = ["string", "comment"] },
+    { start = "\"", end = "\"", close = true, newline = false, not_in = ["string", "comment"] },
+    { start = "'", end = "'", close = true, newline = false, not_in = ["string", "comment"] },
+    { start = "`", end = "`", close = true, newline = false, not_in = ["string"] },
+    { start = "/*", end = " */", close = true, newline = false, not_in = ["string", "comment"] },
+]
+word_characters = ["#", "$", "-"]
+scope_opt_in_language_servers = ["tailwindcss-language-server"]
+prettier_parser_name = "astro"
+prettier_plugins = ["prettier-plugin-astro"]
+
+[overrides.string]
+word_characters = ["-"]
+opt_into_language_servers = ["tailwindcss-language-server"]

extensions/astro/languages/astro/highlights.scm

@@ -0,0 +1,25 @@
+(tag_name) @tag
+(erroneous_end_tag_name) @keyword
+(doctype) @constant
+(attribute_name) @property
+(attribute_value) @string
+(comment) @comment
+
+[
+  (attribute_value)
+  (quoted_attribute_value)
+] @string
+
+"=" @operator
+
+[
+  "{"
+  "}"
+] @punctuation.bracket
+
+[
+  "<"
+  ">"
+  "</"
+  "/>"
+] @tag.delimiter

extensions/astro/languages/astro/injections.scm

@@ -0,0 +1,16 @@
+; inherits: html_tags
+(frontmatter
+  (raw_text) @content
+  (#set! "language" "typescript"))
+
+(interpolation
+  (raw_text) @content
+  (#set! "language" "tsx"))
+
+(script_element
+  (raw_text) @content
+  (#set! "language" "typescript"))
+
+(style_element
+  (raw_text) @content
+  (#set! "language" "css"))