Port to GitHub actions & publish to Terraform registry (#39)

* Port to GitHub actions

* Fix

* Make docs terraform registry compatible

docs/resources/bitbucketserver_user_group.md

@@ -0,0 +1,25 @@
+# Resource: bitbucketserver_user_group
+
+Assign a User to an existing Bitbucket Group.
+
+## Example Usage
+
+```hcl
+resource "bitbucketserver_user_group" "browncoat" {
+  user  = "mreynolds"
+  group = "browncoats"
+}
+```
+
+## Argument Reference
+
+* `user` - Required. User to assign group to.
+* `group` - Required. Group to assign to the user.
+
+## Import
+
+Import a user group reference via the user and group keys:
+
+```
+terraform import bitbucketserver_user_group.browncoat mreynolds/browncoats
+```