Update experimental-features.md (#2175) (#2179)

* Update experimental-features.md

Added title to Experimental features

* Update experimental-features.md

* Update docs/src/appendix/experimental-features.md

Co-authored-by: Megan Wachs <megan@sifive.com>

Co-authored-by: Megan Wachs <megan@sifive.com>
(cherry picked from commit 463a352e

)

Co-authored-by: Abongwa Bonalais <81782853+Burnleydev1@users.noreply.github.com>