Replace the deprecated package coffee-script with coffeescript. Use the version 2, which supports the version 2 of the language.

BREAKING CHANGE: CoffeeScript version 2 is not 100% compatible with the version 1. See https://coffeescript.org/#breaking-changes for more information.

Replace the polyfill with the direct usage of Object.assign.

BREAKING CHANGE: Upgrade Node.js to version 4 or later.

PNPM offers a better performance than NPM.

* The minimum version of Node.js to build and test this package is 12 now.
* Disable some eslint warnings temporarily.

Fix eslint warnings after upgrading eslint.

BREAKING CHANGE: The minimum supported version of Node.js is 8 now.

* Add a simple example of a text project.
* Test the example as a unit test of the preprocessor.

Allow to install coffeescript of the particular version used in the project.

BREAKING CHANGE: The package coffeescript was moved to peer dependencies. If you use a package manager with the feature parity of NPM 8, you won't notice a difference, because it will install the peer depednencies automatically. Otherwise you will need to install coffeescript as a dev dependency, like you did karma earlier.

Use c8 to compute the test code coverage.

Do not distribute development files.