Add categories field to Cargo.toml

[KisaragiEffective]

Added categories field to indicate #![no_std] compatiblity in Cargo.toml. This change makes raw-cpuid visible to category-specific pages (no-std and no-std::no-alloc).

[codecov]

Codecov Report

Merging #160 (8ae4183) into master (0630d77) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #160   +/-   ##
=======================================
  Coverage   36.83%   36.83%           
=======================================
  Files           4        4           
  Lines        4385     4385           
=======================================
  Hits         1615     1615           
  Misses       2770     2770           

[gz]

Thanks!