created deprecated lib

[jedahan]

if we see any of the old variables set

• [ ] print to stderr what changes are needed
• [ ] print to stderr a link to the release announcement in releases
• [ ] try and migrate to new variables so prompt is still semi-functional

[frm]

I'll try to handle this during the weekend.

[jedahan]

Its a one-line warning for now printing to stderr, and a basic migration guide.