Ignore files generated by helm dependency updates

The requirements.lock and tarball generated for oam-kubernetes-runtime
should not be committed to the repository. The lock file specifies a new
timestamp each time it is generated.

Signed-off-by: hasheddan <georgedanielmangum@gmail.com>

.gitignore

@@ -16,4 +16,8 @@ gitlab/
 
 # ignore vscode files (debug config etc...)
 /.vscode
-/.idea
+/.idea
+
+# helm chart dependencies
+**/charts/*.tgz
+**/charts/**/requirements.lock