build/release-nightly: initial commit for release wf in GCB

The artifact .vsix is stored in the PROJECT_ID folder.
  gcloud builds submit \
     --config build/release-nightly.yaml

Change-Id: I20d16ca768cf3113986a1d9386bd96327d3645b7
Reviewed-on: https://go-review.googlesource.com/c/vscode-go/+/461976
Run-TryBot: Hyang-Ah Hana Kim <hyangah@gmail.com>
Reviewed-by: Jamal Carvalho <jamal@golang.org>
TryBot-Result: kokoro <noreply+kokoro@google.com>
diff --git a/build/release-nightly.yaml b/build/release-nightly.yaml
new file mode 100644
index 0000000..10fd4fc
--- /dev/null
+++ b/build/release-nightly.yaml
@@ -0,0 +1,15 @@
+steps:
+# TODO: check build/test status
+#
+# Install dependencies
+- name: node
+  entrypoint: npm
+  args: ['ci']
+# Build .vsix
+- name: node
+  entrypoint: npm
+  args: ['run', 'package']
+artifacts:
+  objects:
+    location: 'gs://$PROJECT_ID/nightly/$BUILD_ID'
+    paths: ['*.vsix']
\ No newline at end of file