Update foundation.md

I am working on making web and game part good in F#. I have successfully ported service stack on heroku using F#. And now working on monogame, nancy ports using F#. And will love to join wonderful F# community.
add F# videos pages
Merge pull request #77 from sergey-tihon/gh-pages

Added "F# For C# Developers" book
Merge pull request #75 from kunjee17/patch-2

Update foundation.md
Merge pull request #76 from TahaHachana/gh-pages

Add videos pages and link on home.