fix: detect legacy 'based on' notices in README.md (#2125)

## PR Checklist

- [x] Addresses an existing open issue: fixes #2124
- [x] That issue was marked as [`status: accepting
prs`](https://github.com/JoshuaKGoldberg/create-typescript-app/issues?q=is%3Aopen+is%3Aissue+label%3A%22status%3A+accepting+prs%22)
- [x] Steps in
[CONTRIBUTING.md](https://github.com/JoshuaKGoldberg/create-typescript-app/blob/main/.github/CONTRIBUTING.md)
were taken

## Overview

🎁

Author: JoshuaKGoldberg

src/options/readReadmeAdditional.test.ts

@@ -72,7 +72,25 @@ After.
 		expect(result).toBe("After.");
 	});
 
-	it("returns all content after contributors when there is a quote template notice", async () => {
+	it("returns all content after contributors when there is a legacy quote template notice", async () => {
+		const getReadme = () =>
+			Promise.resolve(`# My Package
+
+Usage.
+
+<!-- spellchecker:enable -->
+
+After.
+
+> 💙 This package is based on ...
+`);
+
+		const result = await readReadmeAdditional(getReadme);
+
+		expect(result).toBe("After.");
+	});
+
+	it("returns all content after contributors when there is a current quote template notice", async () => {
 		const getReadme = () =>
 			Promise.resolve(`# My Package
 

src/options/readReadmeAdditional.ts

@@ -3,7 +3,7 @@ const indicatorAfterAllContributorsSpellCheck =
 	/<!--\s*spellchecker:\s*enable\s*-->/;
 
 const indicatorBeforeTemplatedBy =
-	/> .* This package was templated with |<!-- You can remove this notice/;
+	/> .* This package (?:is|was) (?:based|build|templated) (?:on|with) |<!-- You can remove this notice/;
 
 export async function readReadmeAdditional(getReadme: () => Promise<string>) {
 	const readme = await getReadme();