Redirect from rule codes to rule pages in docs (#8636)

## Summary

This adds redirects from, e.g., `https://docs.astral.sh/ruff/rules/F401`
to `https://docs.astral.sh/ruff/rules/unused-import`, which are
generated automatically when creating the documentation. Though we want
to move towards human-readable names eventually, I think this is a nice
and user-friendly change (and doesn't require any fancy infrastructure,
since the redirects are handled via a plugin and added client-side).

Closes #4710.

scripts/generate_mkdocs.py

@@ -2,6 +2,7 @@
 from __future__ import annotations
 
 import argparse
+import json
 import re
 import shutil
 import subprocess
@@ -138,9 +139,37 @@ def main() -> None:
 
             f.write(clean_file_content(file_content, title))
 
-    # Add the nav section to mkdocs.yml.
     with Path("mkdocs.template.yml").open(encoding="utf8") as fp:
         config = yaml.safe_load(fp)
+
+    # Add the redirect section to mkdocs.yml.
+    rules = json.loads(
+        subprocess.check_output(
+            [
+                "cargo",
+                "run",
+                "-p",
+                "ruff_cli",
+                "--",
+                "rule",
+                "--all",
+                "--output-format",
+                "json",
+            ],
+        ),
+    )
+    config["plugins"].append(
+        {
+            "redirects": {
+                "redirect_maps": {
+                    f'rules/{rule["code"]}.md': f'rules/{rule["name"]}.md'
+                    for rule in rules
+                },
+            },
+        },
+    )
+
+    # Add the nav section to mkdocs.yml.
     config["nav"] = [{section.title: section.filename} for section in SECTIONS]
 
     with Path("mkdocs.generated.yml").open("w+") as fp: