Release candidate 2.2RC1

What's Changed

• Implement DESTDIR feature by @olebole in #52
• Make Tcl library configurable by @olebole in #60
• Fix manpage location by @olebole in #61
• Make mkpkg customizable by @olebole in #62
• Create dependabot.yml for actions by @olebole in #65
• Bump actions/checkout from 2 to 4 in /.github/workflows by @dependabot in #66
• Fix types and prototypes for gcc-14 by @olebole in #67
• Add Gimp sources for xgterm and ximtool icons by @olebole in #64

Full Changelog: v2.1...v2.2rc1