In RTL the scrollbars are positioned for LTR

### I'm submitting a...
- [x] Bug report
- [ ] Feature request

### Reproduction steps

1. Load EasyMDE with `direction: 'rtl'` in the config
2. In the textarea, type multiple lines until the scrollbar shows, notice the scrollbar is appearing on the right-hand-side when it should be on the left for Left-to-Right languages.

Many of the styles in tinymce css use directional properties for style rules. They should move to logical properties, `inset-inline-start` instead of `left` and so on.

### Version information
Browser type and version: Chrome latest
EasyMDE version: v2.16.1

Reproduce the issue in EasyMDE v2.16.1 using direction: 'rtl' and multiple textarea lines in Chrome. Inspect the directional rules in the TinyMCE CSS, especially scrollbar positioning and left/right declarations. Done means RTL scrollbars and related styles are positioned correctly while LTR behavior remains unchanged.

Written by the indexing model from the issue text.