Non blocking update needed for "super-loop" enjoyers

[HoustonAsh]

I've added 2 new functions:

• asyncUpdate() - essentially doing same thing as update() but in non blocking way
• getEpochTimeMillis() - in some cases I want to use time in milliseconds precision

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[github-actions]

Memory usage change @ 671e503

Board	flash	%	RAM for global variables	%
esp8266:esp8266:huzzah	N/A	N/A	N/A	N/A

Click for full report table

Board	examples/Advanced flash	%	examples/Advanced RAM for global variables	%	examples/AsyncUpdate flash	%	examples/AsyncUpdate RAM for global variables	%	examples/Basic flash	%	examples/Basic RAM for global variables	%	examples/IsTimeSet flash	%	examples/IsTimeSet RAM for global variables	%
esp8266:esp8266:huzzah	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A

Click for full report CSV

Board,examples/Advanced<br>flash,%,examples/Advanced<br>RAM for global variables,%,examples/AsyncUpdate<br>flash,%,examples/AsyncUpdate<br>RAM for global variables,%,examples/Basic<br>flash,%,examples/Basic<br>RAM for global variables,%,examples/IsTimeSet<br>flash,%,examples/IsTimeSet<br>RAM for global variables,%
esp8266:esp8266:huzzah,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A

[github-actions]

Memory usage change @ e370ab6

Board	flash	%	RAM for global variables	%
esp8266:esp8266:huzzah	N/A	N/A	N/A	N/A

Click for full report table

Board	examples/Advanced flash	%	examples/Advanced RAM for global variables	%	examples/AsyncUpdate flash	%	examples/AsyncUpdate RAM for global variables	%	examples/Basic flash	%	examples/Basic RAM for global variables	%	examples/IsTimeSet flash	%	examples/IsTimeSet RAM for global variables	%
esp8266:esp8266:huzzah	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A

Click for full report CSV

Board,examples/Advanced<br>flash,%,examples/Advanced<br>RAM for global variables,%,examples/AsyncUpdate<br>flash,%,examples/AsyncUpdate<br>RAM for global variables,%,examples/Basic<br>flash,%,examples/Basic<br>RAM for global variables,%,examples/IsTimeSet<br>flash,%,examples/IsTimeSet<br>RAM for global variables,%
esp8266:esp8266:huzzah,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A

[HoustonAsh]

should solve #129, #23, #79, #189 (by checking return value of asyncUpdate()),