I'm looking for a function/formula/library that basically takes a MGRS square identifier such as 4QFJ16 and returns me the coordinates of the 4 corners of this polygon in some simple form such as EPSG:4326 lat/lon pair.
The idea behind is that I regularly have data to display where we only know in which square it was taken (no northing/easting information). So I'd simply like to be able to display this specific polygon on a map.
What I can find easily is large graticules as shapefiles, or information to convert a specific point in this square to lat/lon coordinates.
But some "as simple as possible" formula would be better, since I could easily make browser calculations instead of embedding a huge amount of data (the complete graticule). Also, a formula would have the advantage to be language-agnostic, so I can use it for different use cases (realtime JS conversion JS, filling a PostGIS database, ...).
I don't need a huge precision, I work with 10 or 1km MGRS squares.
Hope my question is clear. Many thanks in advance.