When it's a short string, print it inline, otherwise print it
from a separate line. Also add the missing line breaks finally.

With this patch:

Users can now include assets by adding a key-path dictionary
to the configuration as the `assets` field. At build time, Node.js
would read the assets from the specified paths and bundle them into
the preparation blob. In the generated executable, users can retrieve
the assets using the `sea.getAsset()` and `sea.getAssetAsBlob()` API.

```json
{
  "main": "/path/to/bundled/script.js",
  "output": "/path/to/write/the/generated/blob.blob",
  "assets": {
    "a.jpg": "/path/to/a.jpg",
    "b.txt": "/path/to/b.txt"
  }
}
```

The single-executable application can access the assets as follows:

```cjs
const { getAsset } = require('node:sea');
// Returns a copy of the data in an ArrayBuffer
const image = getAsset('a.jpg');
// Returns a string decoded from the asset as UTF8.
const text = getAsset('b.txt', 'utf8');
// Returns a Blob containing the asset.
const blob = getAssetAsBlob('a.jpg');
```

Drive-by: update the  documentation to include a section dedicated
to the injected main script and refer to it as "injected main
script" instead of "injected module" because it's a script, not
a module.

This patch adds support for `sea.getRawAsset()` which is
similar to `sea.getAsset()` but returns the raw asset
in an array buffer without copying. Users should avoid
writing to the returned array buffer. If the injected
section is not marked as writable or not aligned,
writing to the raw asset is likely to result in a crash.

Co-authored-by: Antoine du Hamel <duhamelantoine1995@gmail.com>