pg Dependency missing

While setting up an empty project with pg-listen to do some testing I ran into an issue.

After installing pg listen via `npm i pg-listen` and starting a script with `import createSubscriber from "pg-listen"`, node throws the folloing error:

```
internal/modules/cjs/loader.js:889
const err = new Error(message);
^

Error: Cannot find module 'pg'
Require stack:
- E:\Coding\pg-listener\node_modules\pg-listen\dist\index.js
- E:\Coding\pg-listener\node_modules\pg-listen\index.js
at Function.Module._resolveFilename (internal/modules/cjs/loader.js:889:15)
at Function.Module._load (internal/modules/cjs/loader.js:745:27)
at Module.require (internal/modules/cjs/loader.js:961:19)
at require (internal/modules/cjs/helpers.js:92:18)
at Object. (E:\Coding\pg-listener\node_modules\pg-listen\dist\index.js:56:10)
at Module._compile (internal/modules/cjs/loader.js:1072:14)
at Object.Module._extensions..js (internal/modules/cjs/loader.js:1101:10)
at Module.load (internal/modules/cjs/loader.js:937:32)
at Function.Module._load (internal/modules/cjs/loader.js:778:12)
at Module.require (internal/modules/cjs/loader.js:961:19) {
code: 'MODULE_NOT_FOUND',
requireStack: [
'E:\\Coding\\pg-listener\\node_modules\\pg-listen\\dist\\index.js',
'E:\\Coding\\pg-listener\\node_modules\\pg-listen\\index.js'
]
}
```

After installing the package "pg" manually, the script started successfully.

Having a look into the package.json of pg-listen, "pg" only appears as peerDependency and devDependency.