Updates test project to sls v3 and solve datetime validation issue

[lmammino]

This PR updates the test project to Serverless framework v3

It also closes an issue with the date time validation in the configuration:

• Closes serverless 3 - invalid regular expression error, cannot deploy #76
• Closes fix missing parenthesis for iso regex #78

Finally there are some minor aesthetic improvements:

• Added README in test project
• Updated CI to run also under Node.js 18

[coveralls]

Coverage remained the same at 100.0% when pulling e0b04ad on update-serverless-test-project-to-v3 into ee9ffca on main.

[dchocoboo]

hi, just wondering if this is going to be merged?

[eoinsha]

@dchocoboo We want to add automated testing for serverless@2 and serverless@3 support and plan do to it later this week. In the meantime, is it helpful for you if we publish a pre-release of this branch to npm?

[dchocoboo]

@eoinsha yes please, thank you.
i'll be using it for my production, will feedback if theres any other build issues

[eoinsha]

@dchocoboo 1.1.0-rc1 has been published from this branch. You can install it with

npm install serverless-slic-watch-plugin@next

Great to get your feedback, thank you!

[eoinsha]

@dchocoboo v3 support is now fully available in release 1.1.0