add basic HTTP caching for flights.json
add basic HTTP caching for flights.json

RBE-Avionik/skylines,kerel-fs/skylines,Harry-R/skylines,snip/skylines,RBE-Avionik/skylines,Harry-R/skylines,TobiasLohner/SkyLines,Harry-R/skylines,skylines-project/skylines,Turbo87/skylines,skylines-project/skylines,Harry-R/skylines,Turbo87/skylines,snip/skylines,skylines-project/skylines,Turbo87/skylines,snip/skylines,Turbo87/skylines,shadowoneau/skylines,RBE-Avionik/skylines,shadowoneau/skylines,RBE-Avionik/skylines,shadowoneau/skylines,shadowoneau/skylines,TobiasLohner/SkyLines,TobiasLohner/SkyLines,kerel-fs/skylines,kerel-fs/skylines,skylines-project/skylines