docs: quick start guide improvements

[jcstein]

Suggestion from @msuiche on getting started page:

# Getting Started
## Run Light Node
build/celestia light init
build/celestia light start 
## Get Auth Key
build/celestia light auth admin --p2p.network mainnet
### Write a section about cel-key to explain the difference
### Write a section about the difference between --core.ip and --p2p.network (or change the names into something more explicit)
## Test Client using above
### Rust Client w/ Lumina
### Go Client w/ Normal stuff
## Troubleshooting
### Section about .celestia* folders and the differences

• clear the flags up so they're abundantly clear
  --fullnode.ip --network
• rust could be improved, needs to be updated
• "node tutorial" - title should be more clear

https://docs.celestia.org/how-to-guides/quick-start - I think the updated guide would be good here

A lot of this already exists, just needs to be reorganized and pulled into the quickstart page to improve it