feat: add `--allow-path` and `--manifest` flags

[zshipko]

• A path can be renamed using '=': --allow-path .=/my/new/path
• Or exposed using its existing name: --allow-path .
• Adds --manifest to load manifest from disk instead of WASM module

[nilslice]

Should we use : as the separator, similar to Docker's volume / mount args https://docs.docker.com/storage/volumes/#choose-the--v-or---mount-flag ?