Feat: subfile overrides (#2941)

* Adds overrides parameter to Packer methods and compiler

* Adds tests for overrides parameter

* Update Packer usage examples

docs/usage/packers.md

@@ -2,7 +2,7 @@
 
 > Packers are the way in which `docx` turns your code into `.docx` format. It is completely decoupled from the `docx.Document`.
 
-Packers works in both a node and browser environment (Angular etc). Now, the packer returns a `Buffer`, `Blob` or `base64 string`. It is up to you to take that and persist it with node's `fs`, send it down as a downloadable file, or anything else you wish. As of `version 4+`, this library will not have options to export to PDF.
+Packers works in both a node and browser environment (Angular etc). Now, the packer returns a `Buffer`, `Blob`, `string`, `base64 string`, or `Stream`. It is up to you to take that and persist it with node's `fs`, send it down as a downloadable file, or anything else you wish. As of `version 4+`, this library will not have options to export to PDF.
 
 ### Export as Buffer
 
@@ -14,6 +14,14 @@ Packer.toBuffer(doc).then((buffer) => {
 });
 ```
 
+### Export as string
+
+```ts
+Packer.toString(doc).then((string) => {
+    console.log(string);
+});
+```
+
 ### Export as a `base64` string
 
 ```ts
@@ -32,3 +40,26 @@ Packer.toBlob(doc).then((blob) => {
     saveAs(blob, "example.docx");
 });
 ```
+
+### Export as a Stream
+
+```ts
+Packer.toStream(doc).then((stream) => {
+    // read from stream
+});
+```
+
+### Export using optional arguments
+
+The `Packer` methods support 2 optional arguments.
+
+The first is for controlling the indentation of the xml and should be a `boolean` or `keyof typeof PrettifyType`.
+
+The second is an array of subfile overrides (`{path: string, data: string}[]`). These overrides can be used to write additional subfiles to the result or even override default subfiles in the case that the default handling of these subfiles does not meet your needs.
+
+```ts
+const overrides = [{ path: "word/commentsExtended.xml", data: "string_data" }];
+Packer.toString(doc, true, overrides).then((string) => {
+    console.log(string);
+});
+```