Create `lint` command

Depends on https://github.com/decentraland/sdk/issues/503

Create a linter command that is installed along with the `@dcl/sdk` it should detect that no side effects are executed at root level of the imported files and it should warn about empty imports like `import "./file"` because those are going to be tree shaken.

It also must detect floating promises and fail if those are found.

The `lint` implementation may live inside `dcl-rollup` repository since it is a crucial part of the building process to raise problems as part of the static checks.

The `lint` command should also be accessible via `dcl lint` using the approach suggested at https://github.com/decentraland/sdk/issues/503

The `lint` command will also check for other files, like PNGs and GLTFs for errors. So it should not be entirely bound to a js/ts linter. It may be implemented as a high order function over a regular linter.

Start by reading the dependency issue #503 and the proposed lint implementation location in the dcl-rollup repository. Trace how the command should be exposed through dcl lint and installed with @dcl/sdk. Done requires checks for root-level side effects, empty imports, floating promises, and errors in PNG and GLTF files, with failures reported by the build checks.

Written by the indexing model from the issue text.