Update text and layout to support RTL locales

We don't have active plans to add an RTL locale, but we may do so at some point. Adding notes here for if/when we do so.

- [ ] Add a `dir` attribute.
- [ ] CSS
- Logical properties
- Box shadow
- [ ] HTML classes like `dropdown-menu-right` may need to change.
- [ ] What blocks of text will remain LTR?
- ~"ODK Central" in the navbar~
- What about names and technical terms that are embedded in sentences that are otherwise RTL? Examples: Central, ODK Collect, XForm, XLSForm, Power BI.
- ~Locale names in the locale dropdown~
- pyxform warnings in the `FormNew` component
- Some/all `

` elements?

  - Form ID and version?

  - Submissions table

    - Should we assume that all `string` values are RTL? Or should we set the direction based on the content of the `string`?

    - Should WKT remain LTR?

    - ~What about the direction of numbers? I think that varies even among RTL locales?~

- [x] Do ~numbers and~ dates look correct?

- [ ] Alerts may be a challenge, because they are sometimes in English (if the message comes from Backend), sometimes translated, and sometimes a mix of the two (if a message from Backend is shown next to explanatory text).

  - For a message or part of a message that comes from Backend, we can use the left-to-right isolate Unicode character.

  - Should we use the first strong isolate Unicode character for parts of the message whose directionality is unclear? For example, a project name.

- [ ] Direction of the document title (for example, in the browser tab)