Have Danger check the format of GitHub issue links (#14684)

This PR updates the Danger rules to check for GitHub issue links that
aren't in the desired format:

<img width="916" alt="Screenshot 2024-07-17 at 5 11 48 PM"
src="https://github.com/user-attachments/assets/c77d3c28-3b09-44aa-a97f-03c2400df2e6">

We don't yet check that the links are exactly formatted as expected,
just that they aren't incorrectly formatted in the way that people
typically get it wrong.

Release Notes:

- N/A

script/danger/dangerfile.ts

@@ -33,3 +33,22 @@ if (!hasReleaseNotes) {
     ].join("\n"),
   );
 }
+
+const INCORRECT_ISSUE_LINK_PATTERN = new RegExp("-.*\\(#\\d+\\)", "g");
+
+const hasIncorrectIssueLinks = INCORRECT_ISSUE_LINK_PATTERN.test(
+  danger.github.pr.body,
+);
+if (hasIncorrectIssueLinks) {
+  warn(
+    [
+      "This PR has incorrectly formatted GitHub issue links in the release notes.",
+      "",
+      "GitHub issue links must be formatted as plain Markdown links:",
+      "",
+      "```",
+      "- Improved something ([#ISSUE](https://github.com/zed-industries/zed/issues/ISSUE)).",
+      "```",
+    ].join("\n"),
+  );
+}