add ledger storage snapshots

[tzemanovic]

https://docs.tendermint.com/v0.35/spec/abci/apps.html#taking-snapshots

It would be handy to have some commands for exporting and importing snapshots

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[tzemanovic]

updated link https://docs.tendermint.com/master/spec/abci/apps.html#taking-snapshots

[cwgoes]

Is this still relevant with the deprecation of Tendermint 0.35? What would snapshots help with, exactly?

[tzemanovic]

still relevant with CometBFT - it could be used to speed up block sync