Fix Raku extensions
As Raku documentations says:
Source files generally use the .rakumod extension, and scripts or executables use the .raku. Test files use the .rakutest (or .t) extension. Files which contain documentation use the .rakudoc extension .
Note: The old .p6 (or .pl6), .pm6 (or .pm which is also supported, but discouraged) and .pod6 extensions will continue to be supported for 6.e and marked as deprecated in 6.f
Should be fixed!