Implement the indexer

[Braqzen]

Indexer Guideline

There should be a single wasm module which contains multiple functions, 1 per event. The fn name may follow the pattern index_<event_name>.

E.g.

#[indexer(manifest = "<path/to/file/escrow.manifest.yaml>")]
mod escrow_index {
    fn index_accepted_arbiter_event(event: AcceptedArbiterEvent, block: BlockData) { ... }

    fn index_created_escrow_event(event: CreatedEscrowEvent, block: BlockData) { ... }

    // more events below
}

Each type in graphql should have a required field and use the @indexed directive to allow for easier querying.

From the BlockData we should retrieve the block height and add it to each event so that we have a measure of time for when the event took place.

The indexer should be implemented for the following apps:
[ ] - Escrow
[ ] - AMM
[ ] - Multisig
[ ] - English Auction
[ ] - Airdrop