Add TLDR section to instructions?

[sandeepmistry]

Some feedback from Dominic:

While following the instructions on https://www.arduino.cc/en/Tutorial/FirmwareUpdater

He initially missed the step to load the firmware updater sketch to the MKR1000, and suggested we add a TLDR set to the start of the page: 1) check version 2) install sketch 3) run updater tool

@akash73 @SimonePDA any thoughts on this?

[sandeepmistry]

We should also list the bundled root certificates that are included by default in the firmware: #6 (comment)

[akash73]

I agree!
Simone , can you handle this?