add missing path

[VisenDev]

Because the include directory was not in the paths field of build.zig.zon, building ziglua master as a dependency fails because it fails to find the include directory.

Robert@Roberts-MacBook-Pro-2 ~/z/dev (master)> zig build
install
└─ install dev
   └─ zig build-exe dev Debug native
      └─ translate-c failure
error: error: FileNotFound

error: the following command exited with error code 1:
/Users/Robert/zig/0.13.0/files/zig translate-c -lc --listen=- -I /Users/Robert/zig/dev/.zig-cache/i/a8616f6f48aaff0f313d6060ffcb2711/include /Users/Robert/.cache/zig/p/1220e799b85ed395896173008e6567a5614a4842d1e1485ee62e669926c2082bb93c/include/lua_all.h
Build Summary: 11/15 steps succeeded; 1 failed (disable with --summary none)
install transitive failure
└─ install dev transitive failure
   └─ zig build-exe dev Debug native transitive failure
      └─ translate-c failure
error: the following build command failed with exit code 1:
/Users/Robert/zig/dev/.zig-cache/o/2d41ede4755489dfd1bd6b2e94bb5307/build /Users/Robert/zig/0.13.0/files/zig /Users/Robert/zig/dev /Users/Robert/zig/dev/.zig-cache /Users/Robert/.cache/zig --seed 0x8d01faf -Zd86f12b4e4c6389e

[VisenDev]

Bug introduced in #96

[natecraddock]

Ooo good catch. Thanks!