improve indexer docs

[xmonader]

readme.md

WS_ENDPOINT: is that substrate node url?
START_HEIGHT: how does that affect things?

docker-compose file

document the images used, variables and any concerns (noticed e.g singlenode with insecure flag?)

development.md

it says types.json while it uses typesBundle.json? is it just outdated info?

[DylanVerstraete]

67d140e

[sameh-farouk]

Verification Note:

This wasn't resolved

START_HEIGHT: how does that affect things?

[sameh-farouk]

Addressed in PR #215:

• START_HEIGHT documented in indexer/readme.md and docs/production.md — block height to start ingesting from, 0 = genesis, higher values skip historical blocks
• indexer/development.md title fixed (types.json → typesBundle.json), clarified that typesBundle.json is frozen
• README.md updated: Node v16 → v20, src/types/ described as auto-generated
• All processor env vars documented in docs/production.md
• Docker compose containers reformatted as table with image names and roles