HTTPS Server if TLS_CERT & TLS_KEY are specified

[zohassadar]

I run my local instance of nestrischamps on a computer that isn't my normal desktop, so in order to prevent the browser complaining about permission issues with either the webcam or serial port over HTTP, I bring the server up with a self signed certificate in HTTPS mode. This change modifies server.js to bring up an HTTPS server if a cert file and key file are specified with environment variables. This also modifies the playback link to be HTTPS.

[timotheeg]

Merged after adding a commit to lint!

[timotheeg]

Couple of notes on http vs. https:

• You can develop locally with http with chrome provided in the chrome settings you mark localhost:5000 to be treated as a secure host in the chrome browser settings: chrome://flags/#unsafely-treat-insecure-origin-as-secure
• Providing a local cert as this PR now supports works great, but the renderer may not load in OBS or SLOBS. It seems the browser sources do not like self-signed certificates 🤔
• In "production" the https connectivity is handled by the load balancer, while the server always only handles http