Add external URL linting for markdown files

This commit integrates `remark-lint-no-dead-urls` into the project's
linting process, improving documentation quality by checking for dead
links.

Key changes:

- Add NPM command to verify external URLs in markdown files
- Include new command in the main lint script

Other supporting changes:

- Replace archive.ph link with Wayback Machine for better verification
- Update `remark-lint-no-dead-urls` to latest version (2.0.0)
- Update Browserslist DB to latest to avoid build errors

docs/development.md

@@ -39,6 +39,7 @@ See [ci-cd.md](./ci-cd.md) for more information.
 - Markdown: `npm run lint:md`
 - Markdown consistency `npm run lint:md:consistency`
 - Markdown relative URLs: `npm run lint:md:relative-urls`
+- Markdown external URLs: `npm run lint:md:external-urls`
 - JavaScript/TypeScript: `npm run lint:eslint`
 - Yaml: `npm run lint:yaml`