[suggestions] Ideas to make this github-action more useful

[morficus]

Hello lovely people of Serverless.

This Github Action has been super handy in automating my deployments and I really appreciate that Serverless is offering/hosting an official Github Action. Here are some ideas/suggestions on what I think would help make this action even more useful

1. Let users specify which version of serverless to use: there are 26 forks of this project and about 20 of them (75%) seem to have only done it to change what version used.
2. Indicate what directory to run the command out of (don't assume just the root/base directory): it's fairly common to have a single repository with multiple independent serverless projects which need to be deployed separately.

If you guys are open to contributions and like what I'm suggesting above, I would be willing to open a PR that adds this functionality.
cc: @dschep

[sergioflores-j]

It would be really nice to have this implemented!

Also, caching the installation of Serverless Framework is something to think about, because for every service using this action (if using multiple jobs in the workflow) it installs again and again... adding some extra time at the end of the build process.

But, sadly, it looks like this repo is abandoned by its maintainers :/

[TorbjornHoltmon]

I can't find out how to deploy from a different directory... To be able to decide what directory to deploy from is a must-have feature.

[ryanlawson]

Created a #90 to address these.