message: Add compatibility table
diff: @@ -8,6 +8,20 @@ efficient writing of unit tests, as well as a public API to run contracts in eg.
  go-cosmwasm. As such it includes all glue code needed for typical actions, like
  fs caching.
  +## Compatibility
  +
  +A VM can support one or more contract-VM interface versions. The interface
  +version is communicated by the contract via a Wasm import. This is the current
  +compatibility list:
  +
  +| cosmwasm-vm | Supported interface versions | cosmwasm-std |
  +| ----------- | ---------------------------- | ------------ |
  +| 0.12 | `cosmwasm_vm_version_4` | 0.11-0.12 |
  +| 0.11 | `cosmwasm_vm_version_4` | 0.11-0.12 |
  +| 0.10 | `cosmwasm_vm_version_3` | 0.10 |
  +| 0.9 | `cosmwasm_vm_version_2` | 0.9 |
  +| 0.8 | `cosmwasm_vm_version_1` | 0.8 |
  +
  ## Setup
  There are demo files in `testdata/*.wasm`. Those are compiled and optimized
  