Improves unit-testing development experience by displaying individual
test suite results with the test suite hierarchy.

- modifies `test` script by adding `--verbose` option
- adds `test:watch` script to automatically restart unit tests when source files are modified

Uses `@parcel/transformer-js` to suppress `babel` warnings at compile time.

- adds `transformer` object to `.parcelrc` configuration file

Adds `jest` support and updated `linter` rules.

- updates `eslint` configuration to ignore unused vars starting by `_`

Adds support for the image scaling service provided by IL.

- adds class to generate image scaling URL
- adds test coverage and mock file

This class represents the data model used by `SRGSSR` to describe a media object.
It also provides functions for easy access to the object's properties.

- adds `MediaComposition` class
- adds unit tests
- adds mock files

Allows playback of any unprotected SRG SSR content from its URN.

- adds `DataProvider` which is in charge of retrieving the `MediaComposition`
- adds `SrgSsr` middleware for resolving `srgssr/urn` sources
- updates demo with sample sources
- adds test coverage for `DataProvider` and `SrgSsr` classes
- adds mock files

Resolves #24