write thank you letters/issues to dependencies

[matkoniecz]

• [x] turf - https://github.com/Turfjs/turf - open/close issue should be fine, no other sane way to contact people. Done in https://github.com/Turfjs/turf/issues/2098
• [x] polygon-clipping - https://github.com/mfogel/polygon-clipping/graphs/contributors (emails?)
• [x] osmtogeojson (email, one author) - got response, was appreciated - so it was a good idea to try this
• [x] leaflet - no discussion place, overloaded github... Mentioned twitter account but I will not expose myself to Twitter
• [x] leaflet-draw (abandoned, not sure should I - may be misintepreted as nagging... Hopefully will not be, send.
• [x] d3 - done, via Slack (ugh) but I can make this sacrifice. Yes, I know that it will not be noticed - project is too large