Enable dependabot to automatically update dependencies

[makermelissa]

This has been super helpful with the WebSerial ESPTool repo and I can definitely see it being useful here.

It looks like this will end up being 2 steps:

• Add dependabot to GitHub Actions
• Merge in Dependabot Updates
• Move packages to npm from index.html (if possible) such as xterm and jszip (or another zip package)

[makermelissa]

Fixed via #55 and #77.