feat: switch YAML extension preference from .yml to .yaml (#2310)

## PR Checklist

- [x] Addresses an existing open issue: fixes #2309
- [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

Renames all `.yml` files to `.yaml`, and switches the
[`yml/file-extension`](https://ota-meshi.github.io/eslint-plugin-yml/rules/file-extension.html)
lint rule to its default of `.yaml`.

Also updates `intakeFileAsYaml` to check both `.yaml` and `.yml`,
automatically.

🎁

Author: JoshuaKGoldberg

.github/DEVELOPMENT.md

@@ -52,7 +52,7 @@ Each should be shown in VS Code, and can be run manually on the command-line:
 
 - `pnpm lint` ([ESLint](https://eslint.org) with [typescript-eslint](https://typescript-eslint.io)): Lints JavaScript and TypeScript source files
 - `pnpm lint:knip` ([knip](https://github.com/webpro/knip)): Detects unused files, dependencies, and code exports
-- `pnpm lint:packages` ([pnpm dedupe --check](https://pnpm.io/cli/dedupe)): Checks for unnecessarily duplicated packages in the `pnpm-lock.yml` file
+- `pnpm lint:packages` ([pnpm dedupe --check](https://pnpm.io/cli/dedupe)): Checks for unnecessarily duplicated packages in the `pnpm-lock.yaml` file
 - `pnpm lint:spelling` ([cspell](https://cspell.org)): Spell checks across all source files
 
 Read the individual documentation for each linter to understand how it can be configured and used best.