Support for updating directly from GitHub

[jeremypoulter]

Fixes #259
Fixes #502

[KipK]

Great , thanks for this. I'm enabling it on the UI

[KipK]

That works great,

https://watch.screencastify.com/v/qHl5qp0bJliqgrgkNbth

[KipK]

Perhaps one catch here.

http_update_end doesn't seems to be called at the end ( or missing test if(Update.end(true)) ). not sure but the event["ota"] = "completed" is not published so I suspect this is the case

update doesn't fail btw

[jeremypoulter]

Will take a look

[KipK]

@jeremypoulter, forget it it works. It was testing the wrong ui branch

[KipK]

for proper integration of having daily builds downloaded from the gui v2, I'll wait for ui v2 migration on next major release.
It will need to have the same file names as release to be consistant or at least not 2 versions ( unless we consider we want to keep 2 UI for mid term transitions , but a bit of a pain to maintain )
We should also add the hashed version number as tag instead of "latest" on github this will feed the tag_name properties in :
https://api.github.com/repos/OpenEVSE/ESP32_WiFi_V4.x/releases
and can be used to compare versions on the gui.