[Doc][FAQ] Add a doc for general FAQs to the FAQ folder

## Documentation Scope
Add a doc called 'General Questions' to the FAQ folder created in #612 , answering the questions below:

- [ ] How to connect issues and PRs
- [ ] How are `deployments` and `PRs` associated in DORA?
- [ ] How are `deployments` and `incidents` associated in DORA?
