ci: define and enforce the Zig toolchain policy

README.mdmodified+4-1

Changes to README.md

		⋯755 linesShow the 755 lines above this hunk@@ -756,7 +756,10 @@ zig build examples
756	756
757	757	## Requirements
758	758
759		-- Zig 0.15.1 or later
	759	+- The exact Zig development build recorded in [`.zig-version`](.zig-version)
	760	+
	761	+See [TOOLCHAIN.md](TOOLCHAIN.md) for the compatibility policy and upgrade
	762	+process.
760	763
761	764	## Documentation
762	765