Implement Joplin Alpha Steps UI

### As an author, I want to add steps to a Service Page so that I can transition services to Austin.gov.

**Acceptance criteria**
- [ ] On load, two steps presented by default (and are required fields—see #2180)
- [ ] When user tries to save/publish page with less than two steps, error message: "Service pages must contain at least two steps. If your content does not require steps, please create another page type." *@toribr Where should this error appear? Top of page like other error messages, or inline?*
- [ ] No more than 10 steps may be created *@toribr what should the error message behavior be in this scenario? is this only on page save/publish? Where should this error appear?*
- [ ] The two steps presented by default are "Basic step"
- [ ] Can toggle to a "Step with options" *@toribr In the current implementation, you choose first "basic step" vs. "step with options" but can't toggle once you select.*
- [ ] Content editor must add at least 2 options
- [ ] Content editor can add up to 8 options
- [ ] When content editor adds less than two options, error message appears: "Steps with options must contain at least two options. If your content does not require two options, use Basic Step instead." *@toribr is this only on page save/publish? Where should this error appear?*
- [ ] When content editor adds more than 8 options... *@toribr what should the error message behavior be in this scenario? is this only on page save/publish? Where should this error appear?*
- [ ] When a user enters text into one tab and switches tabs, the text should persist in that tab while a user edits the page (in other words, if user toggles back and forth, will be able to see the text they had previously entered)
- [ ] When the page is saved or published only the tab that is currently selected will be the content that is saved or publishes (content in the non-dominant/current tab is purged)
- [x] Steps can be reordered
- [ ] Basic steps and options have the following rich text capabilities: bullet list, return, links, undo, redo.
- [ ] Basic steps do not allow for ordered list
- [ ] Options do allow for ordered lists

NOTES IN MAGENTA are critical to understanding. Please read them.

See also:
- [Tori/Simi discussion of design and content model](https://github.com/cityofaustin/techstack/issues/675#issuecomment-424072355)
- [WIP Janis design](https://xd.adobe.com/view/cfb1ac5a-4640-4832-4d44-ad95b6fac902-b980/)