Bubble browser languages to top

**Is your feature request related to a problem? Please describe.**
The list of languages is very long and so selecting the post language can be tedious.

**Describe the solution you'd like**
Languages from [`navigator.languages`](https://developer.mozilla.org/en-US/docs/Web/API/Navigator/languages) should be automatically bubbled to the top. (Together with the languages already bubbled up from #101; just use the union of both sets.)

**Describe alternatives you've considered**
The solution in #101 is a first step, but incomplete:
* It requires manual, app-specific configuration for something the user already likely configured globally
* The relationship between these two features (translation and language bubbling) is not obvious
* Even when configured, the two language lists might differ: E.g., I'm not very good in one of the languages in my browser list. Still, I apreciate having the option to have complicated posts in that language translated. (So this language is in `navigator.languages`, but not in the don't-translate list)

**Additional context**
Thank you for creating and maintaining Phanpy!

Start by tracing the post-language selector and the language-bubbling implementation from #101, then inspect how navigator.languages is exposed in the browser. Done means the browser languages and the languages already bubbled by #101 appear together at the top without removing the existing translation-language options.

Written by the indexing model from the issue text.