Setting maxHeight appears to have no effect

**Describe the bug**
Setting {maxHeight: '500px'} in the options appears to have no effect, and the editor continues to adjust height to the content.

**To Reproduce**
Steps to reproduce the behavior:
1. Create a new editor with the option above
2. Fill it with a lot of content
4. See that the editor does not respect the max height.

**Expected behavior**
The editor should expand up to the size defined and then grow now larger, with y overflow scrolling at that point.

** Version information **
- OS: MacOS 11
- Browser: Safari 14 and Chrome 83
- EasyMDE version: 2.10.1

Reproduce the issue in EasyMDE 2.10.1 using a new editor configured with maxHeight: '500px' and enough content to exceed that height. Inspect the editor's sizing and overflow behavior, then verify that it stops growing at the configured maximum and provides vertical scrolling.

Written by the indexing model from the issue text.