[feature] ICAO airport code

[ferdinandhodl]

additional feature, use ICAO airport code, e.g. KJFK (JFK), VTBS (BKK), SBGR (GRU)

[punitarani]

Seems like google flights doesn't natively support this, but can do it with an internal map from ICAO to IATA

[ferdinandhodl]

well g0ggle, - as usual, - is the single point of failure. Professionals from the Airline industry use ICAO codes. g0ggle sucks!

in order to make this work a "translator" module to convert ICAO into IATA could be introduced, - to satisfy g0ggle requests.

[tmchow]

Implemented in #111 - adds an ICAO-to-IATA mapping table so resolve_airport() handles 4-letter codes like KJFK.