Add ADR entry for `ProposeTx` (#1813)
Add ADR entry for `ProposeTx` (#1813)

This adds an ADR entry addressing the implementation of a `ProposeTx`
method in the ABCI proposed in #1776. Fundamentally, this proposal gives
some control of block proposals to the application. The initial use case is
to support the Minimal Viable Plasma specification.
tendermint/tendermint,tendermint/tendermint,tendermint/tendermint,tendermint/tendermint