Dynamic legend for velocity layers

[jtroberts]

Purpose

• Enable dynamic legend with units for velocity layers

Proposed Changes

• Added configuration option to specify legend units
• Dynamic legends based on work done for COGs (similar variable names were left)
• Minor readme updates and updated nvmrc

Issues

• [New Feature]: Visualize velocity data (e.g. wind) as particles or streamlines #596

Testing

• Added velocity streamline layer
• Legend based on colormap automatically appears
• Layer settings now contain color settings to rescale min and max values

[tariqksoliman]

• It looks like the titiler endpoint doesn't like uppercase colormap names:
  • This doesn't work: http://localhost:8888/titiler/colorMaps/RDYLBU_R?format=png
  • But this does http://localhost:8888/titiler/colorMaps/rdylbu_r?format=png
  • I made a new Velocity layer and in the layer config object it's also defined as colorScale: "RDYLBU_R"
• Also not in this PR but it looks like in the configure page the Velocity layers and the Image layers are both using the pink color instead of that sea-foam green.

[sonarqubecloud]

Quality Gate passed

Issues
4 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[tariqksoliman]

LGTM