Print tip about restarting dev server for certain cases (#4535)

This provides guidance within terminal output when running the dev
server, to notify users that the server can be restarted, and should be
for certain editing cases.

Other fixes in this PR:

- Fix formatting elsewhere in `eleventy.config.ts` (this has been
bugging me for a while, but I didn't want to cram it into any bigger PRs
and risk making them more confusing)
- Constrain `eleventyignore` line for `img` folders to only ignore
`*.html`, so changes to images no longer require a dev server restart
(this does not cause any build changes)

Author: kfranqueiro

.eleventyignore

@@ -23,4 +23,4 @@ understanding/*/seizures.html
 **/*-template.html
 
 # HTML files under img will be passthrough-copied
-**/img/*
+**/img/*.html

eleventy.config.ts

@@ -254,7 +254,8 @@ export default async function (eleventyConfig: any) {
     if (runMode === "build" && process.env.WCAG_MODE === "publication") await rimraf("_site");
   });
 
-  eleventyConfig.on("eleventy.after", async ({ dir }: EleventyEvent) => {
+  let hasDisplayedGuidance = false;
+  eleventyConfig.on("eleventy.after", async ({ dir, runMode }: EleventyEvent) => {
     // addPassthroughCopy can only map each file once,
     // but base.css needs to be copied to a 2nd destination
     await copyFile(
@@ -289,6 +290,13 @@ export default async function (eleventyConfig: any) {
       assertIsWcagVersion(version);
       await writeFile(`${dir.output}/wcag.json`, await generateWcagJson(version));
     }
+
+    if (runMode === "serve" && !hasDisplayedGuidance) {
+      hasDisplayedGuidance = true;
+      console.log(
+        "The dev server will restart on TypeScript changes. If you are adding new HTML pages, press Enter to restart it manually."
+      );
+    }
   });
 
   eleventyConfig.setLibrary(
@@ -408,13 +416,11 @@ export default async function (eleventyConfig: any) {
   eleventyConfig.addShortcode("gh", (id: string) => {
     if (/^#\d+$/.test(id)) {
       const num = id.slice(1);
-      return `<a href="https://github.com/${GH_ORG}/${GH_REPO}/pull/${num}" aria-label="pull request ${num}">${id}</a>`
-    }
-    else if (/^[0-9a-f]{7,}$/.test(id)) {
+      return `<a href="https://github.com/${GH_ORG}/${GH_REPO}/pull/${num}" aria-label="pull request ${num}">${id}</a>`;
+    } else if (/^[0-9a-f]{7,}$/.test(id)) {
       const sha = id.slice(0, 7); // Truncate in case full SHA was passed
-      return `<a href="https://github.com/${GH_ORG}/${GH_REPO}/commit/${sha}" aria-label="commit ${sha}">${sha}</a>`
-    }
-    else throw new Error(`Invalid SHA or PR ID passed to gh tag: ${id}`);
+      return `<a href="https://github.com/${GH_ORG}/${GH_REPO}/commit/${sha}" aria-label="commit ${sha}">${sha}</a>`;
+    } else throw new Error(`Invalid SHA or PR ID passed to gh tag: ${id}`);
   });
 
   // Renders a section box (used for About this Technique and Guideline / SC)