Merge pull request #408 from allenai/favyen/20260113-bump-version

bump version to 0.0.21

Author: favyen2

pyproject.toml

@@ -1,6 +1,6 @@
 [project]
 name = "rslearn"
-version = "0.0.20"
+version = "0.0.21"
 description = "A library for developing remote sensing datasets and models"
 authors = [
     { name = "OlmoEarth Team" },