Feature/additional metrics

[luissimas]

Enhance metrics collection. The initial plan was to implement the following features:

1. Check if target is a markdown file
2. Collect word count
3. Collect time to read
4. Exclude links to non existing files
5. Collect backlinks

All features were implemented except for 3 and 4. Time to read can be inferred from word count at query time, giving users more flexibility to use the metrics. Excluding links to non existing files seems a bit too implicit, but it may be added in the future with a configurable option.

The new metrics are now included in the dashboard, producing the following result:

Closes #8.

[codecov-commenter]

⚠️ Please install the to ensure uploads and comments are reliably processed by Codecov.

Codecov Report

Attention: Patch coverage is 72.83951% with 22 lines in your changes missing coverage. Please review.

❗ Your organization needs to install the Codecov GitHub app to enable full functionality.

Files	Coverage Δ
internal/collector/note.go	95.83% <100.00%> (+8.33%)	⬆️
internal/zettelkasten/git.go	7.40% <ø> (ø)
internal/collector/collector.go	63.79% <94.73%> (+8.69%)	⬆️
internal/storage/fake.go	40.00% <0.00%> (ø)
internal/storage/influxdb.go	0.00% <0.00%> (ø)