JS: Update and fix docs, fix Number.toString() with decimals (#4168)

* Update and fix JS docs

This could really use some automation, atleast for API reference
There are TypeScript definitions and typedocs, we don't need to be monkeys copying and reformatting this to API reference by hand

* Fix bugged character

* JS: Fix Number.toString() with decimals

* Fix

* Forgot this one

* docs: mention per-view child format

* Added @portasynthinca3 to docs' codeowners

* Updated CODEOWNERS

---------

Co-authored-by: Anna Antonenko <portasynthinca3@gmail.com>
Co-authored-by: hedger <hedger@nanode.su>
Co-authored-by: hedger <hedger@users.noreply.github.com>

documentation/js/js_gui__file_picker.md

@@ -0,0 +1,20 @@
+# File Picker GUI prompt {#js_gui__file_picker}
+
+Allows asking the user to select a file.
+It is not GUI view like other JS GUI views, rather just a function that shows a prompt.
+
+# Example
+For an example, refer to the `gui.js` example script.
+
+# API reference
+
+## pickFile()
+Displays a file picker and returns the selected file, or undefined if cancelled.
+
+**Parameters**
+  - `basePath`: the path to start at
+  - `extension`: the file extension(s) to show (like `.sub`, `.iso|.img`, `*`)
+
+**Returns**
+
+A `string` path, or `undefined`.