first version

Added

• dcs_coords Python package to convert DCS World map coordinates between
  lat/long (WGS84), DCS planar x, y, MGRS, and UTM.
• Transverse Mercator (WGS84, k₀ = 0.9996) model with exact per-map constants,
  so conversions use real formulas instead of runtime point lists.
• dcs-coords command-line interface: maps (list maps), calibrate
  (add a new map), and generate (rebuild the exports/).
• Bundled maps: Caucasus, Falklands, Mariana Islands, Nevada, Normandy,
  Persian Gulf, Syria, The Channel, Iraq, and Kola.
• Generated exports/ data in JSON, YAML, Python, and Markdown. (from DCS version 2.9.25.21402)
• Documentation under docs/ (adding a map, exports, how it works, developing).