Add FlDotLineSegmentPainter for Enhanced Chart Customization

[JaredEzz]

This pull request introduces a new FlDotLineSegmentPainter to the fl_chart library, expanding the customization options available for dot decorations in line charts. The FlDotLineSegmentPainter is designed to draw a vertical line segment at each data point, with an optional numerical value label displayed above.

Key features and benefits of the FlDotLineSegmentPainter include:

• Customizable Line Segments: Users can specify the color, width, and height of the line segments, allowing for precise control over their appearance.
• Value Labels: Each line segment can be accompanied by a label showing its numerical value, enhancing the informativeness of the chart.
• Optional Labels: The showText parameter enables users to toggle the display of value labels, providing flexibility for minimalistic designs or when labels are not necessary.
• Consistent Style: The painter follows the established coding and commenting conventions of the library, ensuring a seamless integration.

The addition of this painter is particularly helpful for users who require a clear visual distinction between data points, or for those who wish to emphasize the exact value of each point without cluttering the chart with markers.

Example picture:

[imaNNeo]

Oh, it seems a very cool feature!
Actually I think we need to have a catalog of the DotPainters someday somewhere.

Thanks a lot.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.78%. Comparing base (930ac12) to head (e736269).
Report is 14 commits behind head on main.

❗ Current head e736269 differs from pull request most recent head 5c33e55. Consider uploading reports for the commit 5c33e55 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1544      +/-   ##
==========================================
- Coverage   87.52%   86.78%   -0.75%     
==========================================
  Files          45       45              
  Lines        3078     3034      -44     
==========================================
- Hits         2694     2633      -61     
- Misses        384      401      +17     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[imaNNeo]

Oh, it seems there is a formatting issue,
Don't forget to read the contributing guidelines carefully.

[JaredEzz]

Totally my bad! I'm used to Github Actions steps that clean up the formatting for me. Forgive the negligence. All cleaned up now

[imaNNeo]

Can you please rebase your branch?
There are some conflicts