Add instructions on how to add multiple editors to a single page.

Please add instructions on how to add multiple editors to one page. Use code:

~~~
document.addEventListener('DOMContentLoaded', function() {
const easyMDE1 = new EasyMDE({
element: document.getElementById('editor1')
});
const easyMDE2 = new EasyMDE({
element: document.getElementById('editor2')
});
const easyMDE3 = new EasyMDE({
element: document.getElementById('editor3')
});
});
~~~

**Explanation:**
_document.addEventListener('DOMContentLoaded', function() { ... });_ ensures that the JavaScript code runs only after the entire HTML document has been loaded and parsed.
_new EasyMDE({ element: ... });_ creates a new EasyMDE instance. The element option specifies which _textarea_ element to transform into an editor.
You can pass an object with various configuration options to the _EasyMDE_ constructor to customize each editor's appearance and behavior (e.g., _toolbar, spellChecker, autosave_). Refer to the EasyMDE documentation for a complete list of options.

No documentation file or test is named in the issue. Locate the existing EasyMDE documentation entry point, then add the supplied multiple-editor example and explanation. Done means the documentation clearly explains how to initialize multiple editors on one page.

Written by the indexing model from the issue text.