Add support for trend analysis, enriching examples and docs

[Bilpapster]

Description

Add support for trend analysis as part of the data quality measurements (DQMs) suite. Trend analysis is implemented by computing the slope of line that best fits the elements in the window. Implementing this new feature uncovered an small bug regarding the way Pathway (and not) timestamps are handled. This bug is currently out of scope for the current PR but will be fixed soon.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update

Testing

• I have tested this change locally
• I have added tests that prove my fix is effective or that my feature works
• All new and existing tests pass

examples/trend_analysis.py can be executed without external dependencies for testing purposes if needed.

Checklist

• My code follows the project's style guidelines
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation

Fixes #12

[Gatmatz]

Nice job on this! The examples are super clear and make it really easy to follow along.

[Bilpapster]

@Gatmatz good to go? I will need to fix a small style formatting issue that makes automated styling tests to fail. Anything else apart from that? Otherwise I am going to merge it.