(fix) allow boolean or number values in slsw.lib.options

[coyoteecd]

What did you implement:

This change relaxes the types for sls.lib.options object.
Makes it possible to use e.g. boolean options passed via serverless CLI in a typed webpack.config.ts without getting TS compile errors.

For example
const watchEnabled = slsw.lib.options.watch === true; // now gives compile error saying watch must be a string

How did you implement it:

How can we verify it:

Todos:

• Write tests
• Write documentation
• Fix linting errors
• Make sure code coverage hasn't dropped
• Provide verification config / commands / resources
• Enable "Allow edits from maintainers" for this PR
• Update the messages below

Is this ready for review?: YES
Is it a breaking change?: NO

[j0k3r]

Could you rebase against the master? So I'll be able to merge and ship it for 5.5.1. Thanks 🙏

[coyoteecd]

@j0k3r done