Add Continous Integration Build of Firmware Artifacts & Fix Build Script

[calotlea]

Add automated checks for firmware build via Github CI script

Instead of setting up all required development tools locally, let github build the firmware on each push to this repo. If this build fails for any reason an error notifcation is sent. Further the build script also uploads the firmware artifacts to github as part of the workflow, allowing users to fetch the latest push.

The workflow further adds a status badge on the front page of the project indicating build success or failure.

1. Select Actions
2. Select the Firmware workflow
3. Download the latest build artifact

Fix of indefinite build loop in scripts/build_interface.py

When -D EMBED_WWW is commented out it forces pio run --target uploadfs in the python build file. Since the process of pio run hasn't completed and the pre-build script is called again, it just indefinitely recurses in.

Further to reduce noise of regenerated files, WWWData.h and was taken out of version control (was already ignored by .gitignore) but still committed.