feat: add docs for syncing from trusted hash and height

[jcstein]

1. go to ~/.celestia-light-mocha-4/config.toml and change DASer.SampleFrom to the trusted height
2. set --headers.trusted-hash
   cc @S1nus for feedback. is the snapshot still required? or do we JTMB all previous heights < trusted height?

[S1nus]

it just trusts them if you do this

[jcstein]

awesome, makes sense!

[jcstein]

steps from @Bidon15:

1. curl the rpc endpoint for the latest block -1
2. take the hash
3. init the light node with pre-defined config.toml
4. experience immediate success

[jcstein]

1. Get trusted height & hash on Celenium
2. Set the trusted height & hash
   1. Open your config.toml:

   code ~/.celestia-light/config.toml

   1. Set DASer.SampleFrom to the trusted height.
3. Initialize the node store

   celestia light init

4. Run the node

celestia light start --headers.trusted-hash <hash>

[jcstein]

draft info portion for the documentation of this feature:

syncing to a trusted hash means that you will not sample the entire chain. this adds a trust assumption that you trust the history of chain up to that point and that you trust the entity where you get the hash from. in this case, Celenium

[jcstein]

note: if you're using all of these light nodes for similar things like tracking the same rollup, I'd recommend using the same hash/height for them all. you can also skip the celenium part and do step 1 programmatically with a consensus rpc (like the core.ip you provide to a light node, whether it's from a provider or from your own consensus node)

[jcstein]

I think that the above suggestion may not be ideal for fresh nodes:

1. Get trusted height & hash
2. Initialize the node store
   1. celestia light init
3. Set the trusted height & hash
   1. Open your config.toml code .celestia-light/config.toml. Set DASer.SampleFrom to the trusted height (e.g. SampleFrom = 123456)
4. Run the node with the hash and flag:

celestia light start --headers.trusted-hash <hash>