Update .gitpod.dockerfile

Bumps [websocket-extensions](https://github.com/faye/websocket-extensions-node) from 0.1.3 to 0.1.4. **This update includes a security fix.**
- [Release notes](https://github.com/faye/websocket-extensions-node/releases)
- [Changelog](https://github.com/faye/websocket-extensions-node/blob/master/CHANGELOG.md)
- [Commits](https://github.com/faye/websocket-extensions-node/compare/0.1.3...0.1.4)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>

.gitpod.dockerfile

@@ -0,0 +1,7 @@
+FROM gitpod/workspace-full
+
+USER root
+RUN sudo apt-get update && apt-get install -y apt-transport-https \
+ && sudo apt-get install -y \
+    xserver-xorg-dev libxext-dev libxi-dev build-essential libxi-dev libglu1-mesa-dev libglew-dev pkg-config libglu1-mesa-dev freeglut3-dev mesa-common-dev \
+ && apt-get clean && rm -rf /var/lib/apt/lists/* /tmp/*

.gitpod.yml

@@ -1,3 +1,5 @@
+image:
+  file: .gitpod.dockerfile
 tasks:
   - init: npm run setup
     command: npm start