Export all forgotten types

[dawsbot]

This entire task involves adding exports to src/index.ts for the following values.

After completed, the script npm run build:readme should run with zero warnings. Here are the current warnings:

Warning: Modify, defined at src/types/Block.types.ts:3, is referenced by BlockResponse but not included in the documentation.
Warning: RPCBlock, defined at src/types/Block.types.ts:20, is referenced by BlockResponse but not included in the documentation.
Warning: Modify, defined at src/types/Transaction.types.ts:3, is referenced by TransactionResponse but not included in the documentation.
Warning: RPCTransaction, defined at src/types/Transaction.types.ts:4, is referenced by TransactionResponse but not included in the documentation.
Warning: TransactionReceipt, defined at src/types/Transaction.types.ts:34, is referenced by FallthroughProvider.getTransactionReceipt.getTransactionReceipt but not included in the documentation.
Warning: BlockTransactionResponse, defined at src/types/Transaction.types.ts:64, is referenced by BlockResponse.__type.transactions but not included in the documentation.
Warning: ConstructorOptions, defined at src/providers/FallthroughProvider.ts:13, is referenced by FallthroughProvider.constructor.new FallthroughProvider.options but not included in the documentation.
Warning: BlockTag, defined at src/types/Block.types.ts:46, is referenced by FallthroughProvider.getBalance.getBalance.blockTag but not included in the documentation.