docs: update README

[dtbuchholz]

Summary

Updated README with the latest setup steps. Closes #539.

Context

The README was outdated and inaccurate, and we had internal docs already describing the newer steps required.

Implementation overview

N/A

Implementation details and review orientation

N/A

Checklist

• Are changes backward compatible with existing SDKs, or is there a plan to manage it correctly?
• Are changes covered by existing tests, or were new tests included?
• Are code changes optimized for future code readers, commenting on problematic areas to understand (if any)?
• Future-self question: Did you avoid unjustified/unnecessary complexity to achieve the goal?

[dtbuchholz]

I referenced everything from the Notion doc with some tweaks here and there, so lmk if there's anything missing or misinterpreted!

(Note that I originally wanted to keep this README "light" and point to the docs site for much of this, but I wasn't sure how to abstract away the implementation details since all of those setup steps seemed useful.)

[avichalp]

We actually stopped using Ankr because they didn't support Calibration net and we are not live with Filecoin mainnet yet. For Calibration we are using Glif.io.

[dtbuchholz]

@avichalp ahh, that's right. so, i can probably do 2 things:

1. make a callout that Tableland is not live on FIL mainnet yet; this key is shown for demo purposes because when we launch, Ankr is the provider we recommend using (right? iirc, they have the archival support we need)
2. make a callout that for FIL testnet, we use Glif.io. but, they allow for unauthenticated requests, so there's no need to set up a variable like VALIDATOR_GLIF_FILECOIN_CALIBRATION_API_KEY

[avichalp]

so, i think: it would be good to mention that we are not live on mainnet yet. but idk if we want to recommend Ankr yet. i would wait for them to offer the service (full archival node) we need. also, it may happen that Glif.io offers the archival node first (they plan to support it as soon as Lotus fix is ready and have offered us an API key to use it).

also, for the current configuration, we can recommend leaving the Glif API key empty: eg: VALIDATOR_GLIF_FILECOIN_CALIBRATION_API_KEY=

[dtbuchholz]

@avichalp adjusted the README with your feedback—lmk how it looks, and then i can also duplicate this on our docs site if it's 👍

[avichalp]

LGTM 👍