Add OPy regtest links.

This is possible now that we're on the right machine.  Not ideal, but
better than nothing.

doc/release-index.md

@@ -61,6 +61,8 @@ the release.
- [test-gold](test/opy.wwz/test-gold.txt)
- [test-oil-unit-byterun](test/opy.wwz/test-oil-unit-byterun.txt)
- [test-spec-all](test/opy.wwz/test-spec-all.txt)
- [regtest-compile](test/opy.wwz/regtest-compile.txt)
- [regtest-verify-golden](test/opy.wwz/regtest-verify-golden.txt)

Tree-shaking: