[wip upload-image] update readme with new upload-image options

README.md

@@ -148,6 +148,14 @@ easyMDE.value('New input for **EasyMDE**');
 - **promptTexts**: Customize the text used to prompt for URLs.
   - **image**: The text to use when prompting for an image's URL.  Defaults to `URL of the image:`.
   - **link**: The text to use when prompting for a link's URL. Defaults to `URL for the link:`.
+- **uploadImage**: If set to `true`, enables the image upload functionality, which can be triggered by drag&drop, copy-paste and through the browse-file window (opened when the user click on the *upload-image* icon). Defaults to `false`.
+- **imageMaxSize**: Maximum image size in bytes, checked before upload (note: never trust client, always check image size at server-side). Defaults to `1024*1024*2` (2Mb).
+- **imageAccept**: A comma-separated list of mime-types used to check image type before upload (note: never trust client, always check file types at server-side). Defaults to `image/png, image/jpeg`.
+- **imageUploadEndpoint**: The endpoint where the images data will be sent, via an asynchronous *POST* request. The server is supposed to save this image, and if it's successful, return a 200-OK HTTP response containing the relative path of the image. No default value.
+- **imageTexts**: Several string literals used in image-upload features:
+    - **errorImageTooBig**: The error prompted to the user when the size of the image being imported is bigger than the `imageMaxSize`, where `#image_name#`, `#image_size#` and `#image_max_size#` will replaced by their respective values. Defaults to `Image #image_name# is too big (#image_size#).\n' +
+    'Maximum file size is #image_max_size#.`.
+    - **sizeUnits**: A comma-separated list of units used to display messages with human-readable file sizes. Defaults to `b,Kb,Mb`.
 - **renderingConfig**: Adjust settings for parsing the Markdown during previewing (not editing).
   - **codeSyntaxHighlighting**: If set to `true`, will highlight using [highlight.js](https://github.com/isagalaev/highlight.js). Defaults to `false`. To use this feature you must include highlight.js on your page or pass in using the `hljs` option. For example, include the script and the CSS files like:<br>`<script src="https://cdn.jsdelivr.net/highlight.js/latest/highlight.min.js"></script>`<br>`<link rel="stylesheet" href="https://cdn.jsdelivr.net/highlight.js/latest/styles/github.min.css">`
   - **hljs**: An injectible instance of [highlight.js](https://github.com/isagalaev/highlight.js). If you don't want to rely on the global namespace (`window.hljs`), you can provide an instance here. Defaults to `undefined`.