message: fix README link that breaks on npmjs's site
diff: @@ -259,7 +259,7 @@ play with contracts.
  ## Diving into Contracts
  -Check out the [mask documentation](./MASK.md) to view how to use some custom
  +Check out the [mask documentation](https://github.com/cosmos/cosmjs/blob/main/packages/cli/MASK.md) to view how to use some custom
  helpers to upload code and use non-trivial contracts with proper types.
  ## License
  