Move build to use tsdx as build tool

[felixmosh]

This PR moves the build system of the lib to use tsdx.

ps. TSDX utilises github actions as CI

Closes #546

• Title is human readable, as it will be included directly in CHANGELOG.md when we do a release
• If this is a new user-facing feature, documentation has been added to API.md
• Any dist/ changes have not been committed.

Tests run directly on the source code and all dist changes are computed and committed during Formsy release.

[rkuykendall]

This looks really slick. Do you think it's good to go @felixmosh ? Also am I understanding correctly that Travis failing is expected because the project would switch to Github Actions?

[rkuykendall]

Okay wow, I finished reading everything and this looks great. Couldn't find anything to comment on. Some great catches in this PR. Merge when you feel comfortable and then set up the Github Actions?

[felixmosh]

Cool, thanks for the review🙏

[felixmosh]

What will be the best way to release such change?

[rkuykendall]

@felixmosh So the way I build and release is I go into master and I run npm run deploy. The only thing is you need to be added as a maintainer on NPM. Can you send me your NPM username? I'd love to have someone else who is also comfortable with releasing the project.

[felixmosh]

The question was semver wise :]
Is it a breaking change? WDYT?

[rkuykendall]

I mean, technically nothing changes, right? But I guess something could be broken, so let's go with minor?

[felixmosh]

There are changes, "entry" files are different.

BTW, Github actions are enabled :]