Enable watching files remapped by tsconfig paths

[Marcarrian]

We use tsconfig paths to remap locations when debugging our libraries in unit tests:

...
"paths": {
  "my-library": [
    "path-to-my-library"
  ]
}
...

Unfortunately, the files from my-library are not being watched by karma when running unit tests.

In karma.conf.js we have configured esbuild as follows:

...
files: [
  'src/**/*.spec.ts',
],
preprocessors: {
  'src/**/*.ts': ['esbuild'],
},
esbuild: {
  tsconfig: 'path-to-tsconfig/tsconfig.spec.json',
},
...

When using esbuild --watch to bundle the files, the paths specified in tsconfig are respected and a rebuild is triggered on any change.