ERA5 static variables collection asset (#359)

* save

* keep the static var

* Update asset licensing

Author: ghidalgo3

datasets/era5-pds/README.md

@@ -0,0 +1,11 @@
+# ERA5 Collection
+
+## Collection Update
+
+```bash
+pctasks dataset ingest-collection \
+    -d dataset.yaml \
+    -a registry pccomponents \
+    -c era5-pds \
+    --confirm --submit
+```