smalltalkCI integration

[LinqLover]

Students have shown increasing interest in running SwaLint in the CI. However, many of them need to reinvent the wheel because apparently, the interfaces SwaLint are not yet maximally convenient for this use case. For example, overriding coding style preferences for specific code sections and including/excluding specific packages/categories/classes/methods are two requirements for configuration that afaik cannot yet be fulfilled with the built-in support of SwaLint. See also #85. It could be helpful to provide a new or refined TestCase interface in SwaLint to facilitate CI usage.

Hypothetically, we could even make a PR to smalltalkCI to add a small hook in configuration there to trigger the linter independently of the actual test suite(s).

For further inspiration, existing specification approaches such as eslintrc should be considered. We could also collect all projects that currently use SwaLint here to evaluate their greatest common divisor.