Add Homepage to docs - Githubissues

Adding homepage to docs. Added ref to homepage in both index.md and mkdocs.yml. Added page under ...apps.

[x] App documentation page created
[x] markdownlint reports no errors on edited page(s) - use https://dlaa.me/markdownlint/ if your IDE does not have this built in
[x] Reference added in docs/sandbox/index.md
[x] Reference added in mkdocs.yml nav menu

saltyorg / docs