chore: Extract languages from zed crate (#8270)

- Moves languages module from `zed` into a separate crate. That way we
have less of a long pole at the end of compilation.
- Removes moot dependencies on editor/picker. This is totally harmless
and might help in the future if we decide to decouple picker from
editor.

Before:
```
Number of crates that depend on 'picker' but not on 'editor': 1
Total number of crates that depend on 'picker': 13
Total number of crates that depend on 'editor': 30
```
After:
```
Number of crates that depend on 'picker' but not on 'editor': 5
Total number of crates that depend on 'picker': 12
Total number of crates that depend on 'editor': 26
```
The more crates depend on just picker but not editor, the better in that
case.

Release Notes:

- N/A

crates/languages/src/markdown/config.toml

@@ -0,0 +1,14 @@
+name = "Markdown"
+grammar = "markdown"
+path_suffixes = ["md", "mdx"]
+word_characters = ["-"]
+brackets = [
+    { start = "{", end = "}", close = true, newline = true },
+    { start = "[", end = "]", close = true, newline = true },
+    { start = "(", end = ")", close = true, newline = true },
+    { start = "<", end = ">", close = true, newline = true },
+    { start = "\"", end = "\"", close = false, newline = false },
+    { start = "'", end = "'", close = false, newline = false },
+    { start = "`", end = "`", close = false, newline = false },
+]
+prettier_parser_name = "markdown"

crates/languages/src/markdown/highlights.scm

@@ -0,0 +1,24 @@
+(emphasis) @emphasis
+(strong_emphasis) @emphasis.strong
+
+[
+  (atx_heading)
+  (setext_heading)
+] @title
+
+[
+  (list_marker_plus)
+  (list_marker_minus)
+  (list_marker_star)
+  (list_marker_dot)
+  (list_marker_parenthesis)
+] @punctuation.list_marker
+
+(code_span) @text.literal
+
+(fenced_code_block
+  (info_string
+    (language) @text.literal))
+
+(link_destination) @link_uri
+(link_text) @link_text

crates/languages/src/markdown/injections.scm

@@ -0,0 +1,4 @@
+(fenced_code_block
+  (info_string
+    (language) @language)
+  (code_fence_content) @content)

crates/languages/src/markdown/outline.scm

@@ -0,0 +1,5 @@
+(atx_heading
+    .
+    (_) @context
+    .
+    (_) @name ) @item