Housekeeping

[nikku]

Proposed Changes

Modernizes the basic setup around this library:

• Updates to ESM + CJS module
• Bumps dependencies
• Gets rid of a lot of cruft
• Introduces GitHub CI action

Checklist

To ensure you provided everything we need to look at your PR:

• [x] Brief textual description of the changes present
• [ ] Visual demo attached
• [ ] Steps to try out present, i.e. using the @bpmn-io/sr tool
• [ ] Related issue linked via Closes {LINK_TO_ISSUE} or Related to {LINK_TO_ISSUE}

[nikku]

There is more stuff to be done, i.e. to turn this library into a true dual ESM/CommonJS module. But that would require to fix the upstream (broken, bundling wise) diffpatch library. To be done another day.