Heatmap on arc-green theme looks out of place

[atomicptr]

• Gitea version (or commit ref): 2ce72d4
• Can you reproduce the bug at https://try.gitea.io:
  • Yes (provide example URL)
  • No
  • Not relevant

Description

As you can see in the screenshot below the heatmap doesn't look like it probably should when using the arc-green theme.

Screenshots

[SagePtr]

I think heatmap should use different transparency of green rather than gradient from white to green.

[sapk]

The libs seems to support custom gradient. The colorRange option could be a ui option of gitea to set along the theme.
https://github.com/DKirwan/calendar-heatmap