Split fontique into its own package.

[xStrom]

This PR will:

• Take the fontique module and split it into its own package.
• Add README.md for fontique.
• Polish the Cargo.toml files, including proper feature dependency specifications. Previously libm was always enabled, even with std.
• Take another couple of steps towards making no_std work by introducing the use of the no_std attribute and adding the CI steps to test it. Plus the code changes required to get things to compile.
• Bring the MSRV back to 1.70 in light of Bump fontconfig-cache-parser #36 being merged.

[dfrg]

This is great and I really appreciate all the work you’ve done to clean up the mess.