Use psa for compiling if installed

[f-f]

Description of the change

This detects if psa is installed in the system and if so automatically uses it to compile.

Also adds a global --no-psa flag to disable this.

Closes #283 (which this supersedes)

Checklist:

• Added the change to the "Unreleased" section of the changelog
• Added some example of the new feature to the README
• Added a test for the contribution (if applicable)

[i-am-the-slime]

Does it work with a local psa in node_modules?

[stkb]

@i-am-the-slime No, nor does it for purs, and it's something that probably should be added.