feat: run-rust-backtick lint

Use srgn[1] to find comments that contain empty backtick pairs which
vscode is happy to add.

[1]: https://github.com/alexpovel/srgn

.pre-commit-hooks.yaml

@@ -155,3 +155,12 @@
   pass_filenames: false
   minimum_pre_commit_version: 0.15.0
   description: "Runs buf breaking at the repo root"
+
+- id: rust-doc-backticks
+  name: "rustdoc backticks"
+  entry: run-rust-backticks.sh
+  language: "script"
+  files: \.rs$
+  pass_filenames: true
+  minimum_pre_commit_version: 0.15.0
+  description: "Check for empty backtick pairs"

run-rust-backticks.sh

@@ -0,0 +1,12 @@
+#!/usr/bin/env bash
+
+# Find comments with empty backtick pairs (`thing``).
+#
+# Expects filenames to validate as script arguments.
+
+set -euo pipefail
+
+srgn -j --fail-no-files -G "$@" \
+	--rust doc-comments \
+	--rust comments \
+	'[^`]`{2}[^`]+'