Add v0.26.2 release notes
Add v0.26.2 release notes

This is a strange minor release that was done to fix the Windows build,
but otherwise doesn't have any functional changes, so this only updates
the release notes.

See https://github.com/loadimpact/k6/commit/459da79ef51b37e5eaba4575c9065d9e592e5c49

loadimpact/k6,loadimpact/k6