Repository: JoshuaKGoldberg/create-typescript-app (ts)

Issue:
🐛 Bug: README.md additional content should ignore older "this package is based on" notices
### Bug Report Checklist

- [x] I have tried restarting my IDE and the issue persists.
- [x] I have pulled the latest `main` branch of the repository.
- [x] I have [searched for related issues](https://github.com/JoshuaKGoldberg/create-typescript-app/issues?q=is%3Aissue) and found none that matched my issue.

### Expected

Older CTA repos used "templated by" notice like:

```md
> 💙 This package is based on [@JoshuaKGoldberg](https://github.com/JoshuaKGoldberg)'s [create-typescript-app](https://github.com/JoshuaKGoldberg/create-typescript-app).
```

This should be omitted when running `npx create-typescript-app` in transition mode

### Actual

https://github.com/JoshuaKGoldberg/should-semantic-release/pull/547/files#r2026952619: it's not.

### Additional Info

🎁 

Pull request description:
fix: detect legacy 'based on' notices in README.md
## 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

🎁 

Patch:
diff --git a/src/options/readReadmeAdditional.ts b/src/options/readReadmeAdditional.ts
index b7a485e..a06eb58 100644
--- a/src/options/readReadmeAdditional.ts
+++ b/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();


Test patch:
diff --git a/src/options/readReadmeAdditional.test.ts b/src/options/readReadmeAdditional.test.ts
index 76bc78b..707c671 100644
--- a/src/options/readReadmeAdditional.test.ts
+++ b/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