Add, edit, view experience and connect to backend

[marcusgchan]

Description

• Closes #2 and #8
• Connected the frontend to backend by fixing some of the expected properties since the frontend and backend expected different values

Some examples were:

Frontend expected percent for grades (86%, ...) Backend expected a letter grade (+A, A, ...)

Frontend end_date expected " " Backend end_date expected " " or "Present"

Fix was I added a checkbox:

[dtemir]