enh: add a list of known nvidia drivers as an attr in nixGL

known_drivers/README.md

@@ -0,0 +1,10 @@
+# Nvidia drivers
+
+A single nix expression listing known nvidia driver versions and their corresponding hashes.
+To be used as input to flakes that use nixGL
+
+The list of version/hash pairs can be regenerated by the `mk-nvidia-drivers.py` script,
+which fetches the list of drivers at https://download.nvidia.com/XFree86/Linux-x86_64/
+for each version, attempts to locate a runfile using the same url template as used to
+generate the nixGLNvidia wrappers, then run nix-prefetch-url to get the hash, then
+cleans the downloaded runfile out the store.