Embed static resources

[Deleplace]

Suggestion: let's use the go package embed to produce a self-contained "fat binary" app executable.

Pros:

• follows modern best practices (since Go 1.16)
• single file copied into the final docker image
• minimizes potential attack surface
• avoids bugs like #98

I can make a PR for this.

[grayside]

This makes sense to me.