Update repo name to bee-app

[mmurad2]

Context
The stack terminology causes confusion as this repo is a does not capture the entire Bee Stack. We also discussed moving away from the "stack" terminology in general.
For this specific repo, "app" seems more appropriate.

To dos

• Update repo name
• Update readme to replace bee stack to bee app
• Update other i-am-bee repo readmes that reference the bee-stack

[geneknit]

Removed @jezekra1 and marked with question @mmurad2