clarify WSL, reformat `ps3dev` mentions

Added WSL clarification. No real need for PS3DEV to be constantly referred to as `ps3dev` in retrospect - the headings call it PS3DEV.

avoid potential env pitfall

in the guide, it should be clearer that the terminal must re-read the profile to load the variables. minor edit - not worth its own PR - but sufficiently important, as one user has already fallen to this problem.

Create test-release.yml

Add build scripts (#3)

Make `ps3dev` the sole orchestrator, and give it scripts to build each stage and package them together.

CI: build from ps3dev scripts

Update README.md

Package full release from precompiled toolchain (#2)

* Add GitHub Actions workflow for PS3 SDK release

* Refactor GitHub Actions workflow for PS3 SDK build

* Enable macOS runners in build workflow