Add IsConnected implementation to ESP8266

[kammce]

• This implemenation does not work on older firmware esp8266
• Add ReadRaw() to esp8266 to allow for a non-blocking method of reading data from the serial port directly.
• Modify example project to use ReadRaw after 1 second delay
• Make UART0 buffer 2kB
• Make esp8266 uart buffer 2kB
• Make lpc40xx uart default to 2kB

[codecov[bot]]

Codecov Report

Merging #1450 (6b55144) into master (db38d4b) will not change coverage. The diff coverage is n/a.

@@          Coverage Diff           @@
##           master   #1450   +/-   ##
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  Coverage    59.8%   59.8%           
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  Files          94      94           
  Lines        4516    4516           
  Branches      970     970           
======================================
  Hits         2698    2698           
  Misses       1589    1589           
  Partials      229     229           

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