Rework build process

[CGNonofr]

The Goal of this PR is fix those issues:

• The library only exports the code in UMD format
• When using it in the browser, the code contains references to fs and path directly and also includes the node version of tensorflow that imports crypto)

What the PR does:

• It replaces webpack with rollup to be able to output ESM
• it exports 3 formats:
  • The current node UMD format for backward compability (with same format/terser configuration/sourcemap)
  • A new node ESM format
  • A new browser ESM format

[CGNonofr]

Is there anything I can do to help moving forward on it?

[CGNonofr]

up?

[CGNonofr]

is this project unmaintained?