[gitpod] fix #4832: enable electron testing

.gitpod.dockerfile

@@ -0,0 +1,17 @@
+FROM gitpod/workspace-full-vnc:latest
+
+USER root
+# Install custom tools, runtime, etc.
+RUN apt-get update \
+    && apt-get install -y libx11-dev libxkbfile-dev \
+    && apt-get clean && rm -rf /var/cache/apt/* && rm -rf /var/lib/apt/lists/* && rm -rf /tmp/*
+
+USER gitpod
+# Apply user-specific settings
+RUN bash -c ". .nvm/nvm.sh \
+    && nvm install 10 \
+    && nvm use 10 \
+    && npm install -g yarn"
+
+# Give back control
+USER root

.gitpod.yml

@@ -1,7 +1,9 @@
+image:
+  file: .gitpod.dockerfile
 ports:
 - port: 3000
 tasks:
-- init: nvm install 10 && nvm use 10 && yarn
+- init: yarn
   command: yarn --cwd examples/browser start ../..
 github:
   prebuilds: