Add geo-utils-cpp to Misc

[gistrec]

Adds geo-utils-cpp — a header-only
C++17 library for spherical (lat/lng) geometry on Earth coordinates:
distance, bearing, polygon area, point-in-polygon, and path proximity.

• License: Apache-2.0
• No runtime dependencies
• C++17, CMake 3.14+ (imported target geo::utils)
• CI on Linux (gcc/clang), macOS, Windows; downstream find_package
  smoke-tested on all three

Inserted alphabetically in Libraries → Misc between Font Chef
and HashLibPlus. There's no dedicated geometry/GIS subsection, and
"Misc" is where similarly-scoped libraries (date, EnTT, Magic Enum, …)
live.

Note: this PR was originally opened as geo-utils; the project was
renamed to geo-utils-cpp to avoid a Repology naming conflict
(see gistrec/geo-utils-cpp#11). The branch has been force-pushed
to use the new name.