add EJS_screenCapture (#62)

* add `EJS_screenCapture`

* clarify docs

* random c

* rename to upscale

Author: allancoding

content/1.docs/7.options.md

@@ -481,12 +481,36 @@ Sets the location of what buttons. More information about the virual gamepad but
 ### `EJS_controlScheme`
 
 - Type: `string`
-- Default: ``
+- Default: ` `
 
 Default behaviour (when option is undefined) not changed (core name will be used).
 
 Available control schemes: `nes` `gb`  `gba` `snes` `n64` `gba` `nds` `vb` `segaMD` `segaCD` `sega32x` `segaMS` `segaGG` `segaSaturn` `3do` `atari2600` `atari7800` `lynx` `jaguar` `arcade` `mame`
 
+### `EJS_screenCapture`
+
+Changes the default settings and buttons in the toolbar for screenshots and video recording.
+
+- Type: `object`
+- Default/Example:
+
+```js
+EJS_screenCapture = {
+    photo: {
+        source: "canvas", // or "retroarch" (note: setting to retroarch will ignore the format and just be png)
+        format: "png", // can also be `jpeg` or `webp` (note: safari doesn't support webp so it will default back to png if set)
+        upscale: 1 // can also be `0` which is native, any positive # is valid (note: this will upscale the canvas & frame size by this number).
+    },
+    video: {
+        format: "detect", // checks in order of `mp4` then `webm` to see if it's supported in the browser (note: will default to what is first supported)
+        upscale: 1, // any positive # is valid (note: this will upscale the canvas & frames size by this number).
+        fps: 30, // can also be 60
+        videoBitrate: 2621440, // can be any valid bitrate.
+        audioBitrate: 196608 // can be any valid bitrate.
+    }
+}
+```
+
 ### `EJS_Buttons`
 
 #### Version 4.2.1 and earlier