Add page for exercise info and text

[shreyapandit]

Jenny to curate text for Squat and Heel raise

1. Add a template for the page in Anchor
2. Add routes and navigation for the same
3. Fetch text from exercise table
4. incorporate video/visual with Bootstrap modal
5. update UI to include entry form for exercise info
6. create POST route and update MongoDB model to include new exercise data

[shreyapandit]

Good to have if we have bandwidth to do it before July