hex grid plots using h3pandas

[armstrys]

@dadofsambonzuki just wanted to share what I was playing with this weekend. When I installed h3 on my system using the requirements.txt in this PR I was getting an error when trying to generate the h3 geometry using poly fill. I am honestly not confident that this implementation gives the same result as yours...

From reading about h3 it seems like their resolution scale is defined from 0-15 and doesn't have a direct physical meaning (like degrees or km). I also was only able to get h3 to run in WGS84 (units degrees) and not web mercator (units area). Right now this code is building a grid at scale 2 (very coarse), aggregating, converting to web mercator and then calculating area/density. Because the CRS is so warped in many parts of the map I expect there is quite a bit of error in the area calculation. This should be less of an issue as the hex size gets smaller. I am guessing the version of the code you had running before was aggregating at scale 8, which is probably more appropriate for an interactive map, but wasn't displaying the static plot

[armstrys]

and I am just now seeing that the files in [merchant-density-hex](https://github.com/teambtcmap/btcmap-data/tree/main/data-analysis/merchant-density-hex) are different and those do run on my system and generate a geojson! I added a geojson output to this new implementation as well