Inconsistent-looking `require` module paths.

Currently all the module paths are written in relative paths, which looks inconsistent across the codebase, and is one extra mental burden to keep track of. e.g. in [main.js](https://github.com/Automattic/dot-handy/blob/trunk/main.js#L9):

```
const {
setLocalStorage,
initialize,
} = require( './lib/init.js' );
const { readConfigFiles, mergeConfig } = require( './lib/config.js' );
const { readActionFiles } = require( './lib/action.js' );
const { getRootUrlFromEnv, parseNonSpaceSeparatedList } = require( './lib/misc.js' );
```

in any of the action files, e.g. [close-action.js](https://github.com/Automattic/dot-handy/blob/trunk/actions/close-account.js#L1):
```
const { createAction, readActionFile } = require( '../lib/action.js' );
```

It'd be better if the module searching path can be set like Calypso does.

Start with the require examples in main.js and actions/close-account.js, then inspect how Calypso sets its module search path. Determine the project-wide approach for replacing the inconsistent relative paths, and verify that module loading still works throughout the codebase.

Written by the indexing model from the issue text.