[Playground] Event selection

[justinyoo]

AS a logged in user
I WANT to select an event from the list
SO THAT I can access to the playground page

ASSUMPTION: The user has already logged in with their GitHub ID

[justinyoo]

1. [OpenAPI] Add endpoint for list of events #179
2. [Backend API] Implement endpoint for list of events #180
3. [Playground] Component - list of events (UI only) #181
4. [Playground] Component - list of events (UI logic only) #224
5. [Playground] Component - list of events - page redirection #182