fix(.gitpod.yml): use lts node (#49382)

* fix: use lts node in gitpod

* fix: use custom Dockerfile

* fix: actually use the image...

.gitpod.Dockerfile

@@ -0,0 +1,8 @@
+FROM gitpod/workspace-mongodb:latest
+
+# from https://www.gitpod.io/docs/introduction/languages/javascript#node-versions
+RUN bash -c 'VERSION="lts/*" \
+    && source $HOME/.nvm/nvm.sh && nvm install $VERSION \
+    && nvm use $VERSION && nvm alias default $VERSION'
+
+RUN echo "nvm use default &>/dev/null" >> ~/.bashrc.d/51-nvm-fix

.gitpod.yml

@@ -1,4 +1,5 @@
-image: gitpod/workspace-mongodb
+image:
+  file: .gitpod.Dockerfile
 ports:
   - port: 27017 # mongodb
     onOpen: ignore