feat: add tests and CI, update types and use pool.run() instead of pool.runTask()

[darkgl0w]

Hello.

This PR aims to :

• add GitHub action CI
• swap the deprecated pool.runTask() with pool.run().
• update typescript definitions (fix Updates to plugin.d.ts to support Fastify v3 #7) and add types tests.
• update examples server code.
• update package dependencies.
• add tests to the package.

Note: typescript users may face issues when using fastify < 3.x, maybe we should also update the plugin.js fastify minimum required version field to >= 3.0.0.

Feel free to ping me if changes are required. ^^

[lucastasio]

Hi everyone and, above all, thanks in advance.
Since the request has been approved, is it possible to merge it with the current branch?
Thank you, again.

[joshuagame]

Thank you so much @metcoder95.