ci: adjust release page generation

This change is a POC to address JoshuaKGoldberg/create-typescript-app#1913.  Since it's not something we can really test locally, I figured we test it out here, and then, if successful, I can make the updates upstream.

Here we've changed the release-it config from json to js, which allows us to create a custom function for `github.releaseNotes`.  Using the context provided by release-it, we can filter by groups that we want to keep, and organize them into the same groups that we're organizing for the CHANGELOG (via conventional-changelog)

.release-it.js

@@ -1,30 +1,60 @@
-{
-	"git": {
-		"commitMessage": "chore: release v${version}",
-		"requireCommits": true
+module.exports = {
+	git: {
+		commitMessage: "chore: release v${version}",
+		requireCommits: true,
 	},
-	"github": {
-		"autoGenerate": true,
-		"release": true,
-		"releaseName": "v${version}"
+	github: {
+		release: true,
+		releaseName: "v${version}",
+		releaseNotes(context) {
+			const groupTitles = {
+				feat: "Features",
+				fix: "Bug Fixes",
+				perf: "Performance Improvements",
+			};
+			const commits = context.changelog.split("\n").slice(1);
+			const groups = Object.groupBy(commits, (commit) => {
+				// If it matches one of the types we care to show, then add the
+				// commit to that group.
+				for (const type in groupTitles) {
+					const regex = new RegExp(`^\s*[-*]?\s*${type}[(:]`);
+					if (regex.test(commit)) {
+						return type;
+					}
+				}
+
+				// If it didn't match any of the important groups, then add it to other
+				return "other";
+			});
+
+			// Use the data we've collected to build the release notes.
+			const releaseNotes = [];
+			for (const type in groupTitles) {
+				if (groups[type]) {
+					releaseNotes.push(`### ${groupTitles[type]}`);
+					releaseNotes.push(...groups[type]);
+				}
+			}
+			return releaseNotes.join("\n");
+		},
 	},
-	"npm": { "publishArgs": ["--access public", "--provenance"] },
-	"plugins": {
+	npm: { publishArgs: ["--access public", "--provenance"] },
+	plugins: {
 		"@release-it/conventional-changelog": {
-			"infile": "CHANGELOG.md",
-			"preset": "angular",
-			"types": [
-				{ "section": "Features", "type": "feat" },
-				{ "section": "Bug Fixes", "type": "fix" },
-				{ "section": "Performance Improvements", "type": "perf" },
-				{ "hidden": true, "type": "build" },
-				{ "hidden": true, "type": "chore" },
-				{ "hidden": true, "type": "ci" },
-				{ "hidden": true, "type": "docs" },
-				{ "hidden": true, "type": "refactor" },
-				{ "hidden": true, "type": "style" },
-				{ "hidden": true, "type": "test" }
-			]
-		}
-	}
-}
+			infile: "CHANGELOG.md",
+			preset: "angular",
+			types: [
+				{ section: "Features", type: "feat" },
+				{ section: "Bug Fixes", type: "fix" },
+				{ section: "Performance Improvements", type: "perf" },
+				{ hidden: true, type: "build" },
+				{ hidden: true, type: "chore" },
+				{ hidden: true, type: "ci" },
+				{ hidden: true, type: "docs" },
+				{ hidden: true, type: "refactor" },
+				{ hidden: true, type: "style" },
+				{ hidden: true, type: "test" },
+			],
+		},
+	},
+};