README.md: add Github build badge
Change-Id: I46053977f457dd0f53106ddf15fbc4351dd92d3a
Reviewed-on: https://cue-review.googlesource.com/c/cue/+/3544
Reviewed-by: Marcel van Lohuizen <mpvl@golang.org>
diff --git a/README.md b/README.md
index c04d415..e67c6c0 100644
--- a/README.md
+++ b/README.md
@@ -14,6 +14,7 @@
limitations under the License.
-->
[](https://godoc.org/cuelang.org/go)
+[](https://github.com/cuelang/cue/actions)
[](https://goreportcard.com/report/github.com/cuelang/cue)
[](https://golang.org/dl/)
[]()