Add Windows-compatible Makefile for hdbscan-cpp

[qubitslabs]

his pull request adds a Makefile.windows for Windows users who want to build the project using g++ (via Git Bash, MSYS2, or MinGW). The original Makefile uses Linux-specific commands (find, rm), which fail on Windows systems.

Changes:

Replaced find with wildcard

Used del instead of rm

Added Makefile.windows instead of modifying the original file to avoid affecting Linux users