[Feature] Add Average for Download, Upload, Ping

[svenvg93]

📃 Description

This PR introduces new functionalities and updates the data display on the dashboard.

🪵 Changelog

➕ Added

• Add an Average line line to the Download, Upload & Ping Charts. Which shows the average over the selected time frame, but only when there is 2 or more data points in that time frame.
  - To close Displaying averages + deltas #243
  - to close Adding a New Feature for Tracking Average WAN Speeds #1244
  - to close [Feature Req] Please utilise text based min / max / avg summary, same as HenryWhittaker version #1408
  - to close More Statistics like variance #1194

✏️ Changed

📷 Screenshots

[jwaugh]

THANK YOU SO MUCH FOR IMPLEMENTING THIS FEATURE!!! IT SHOULD HAVE ALWAYS BEEN INCLUDED. I LOVE IT!!!!!!!!

Sorry, not sorry for shouting! I'm so happy! I have wanted this feature since I started using your app. Actually, I believe there was a time when it did tell you the average in text. I've used it that long. hahaha. Thank you again, @alexjustesen! This is one of my favorite pieces of home lab software to keep track of my Frontier Fiber internet and make sure my WAS-110 is doing alright and giving me full provisioned speeds.