Localize internal links

**Describe the bug**
When you add an internal link in Spanish, it inserts the title in English as well as the English URL.

This is going to start to get problematic as we add more internal links and have the ability to change slugs. We're currently using external links for all links within rich text blocks to alpha.austin.gov pages; we'll need to switch this once it's all fixed.

**URL**
Joplin staging

Watch this video to see the bug: https://drive.google.com/open?id=1EL8L51tttCcaN0FLjGRyB9jw7yJwWGMK

**To Reproduce**

1. Edit a page in Spanish
2. Add an internal link to a rich text block using the internal link picker
3. Preview the page
4. See error

**Current behavior**
Links you just added go to the English version, and have the English title in the text (if you didn't specify different text)

**Expected behavior**
- [ ] When adding an internal link in Spanish, the default text is the Spanish title
- [ ] When you add an internal link to a page in Joplin, in Janis it links to the Spanish URL (has `es` in the URL)

**Screenshots**

**Device**

**Browser**

**Additional context**