add baseline translation support for the chooser

[possumbilities]

Description

• fixes: the wp cli i18n command encounters errors when trying to manipulate files #186
  • amends docker-compose.yml to mount the vocabulary-theme src directory appropriate, and sets working_dir to that directory in the wordpress-cli section
• adds baseline transifex.yml configuration file
• setups up new src/languages dir
• generates initial src/languages/vocabulary-theme.pot file
• wraps all possible interface strings in static-chooser.php (minus marking statements) for WordPress appropriate gettext string extraction via wpcli
  • if we also want to provide translations of the marking statements in their various formats then we first need to update the Chooser UX to support the ability to showcase the original english statement alongside the translated statement so that people are given the option of output. It is feasible someone might want to generate an English marking statement, but utilize the UX of the chooser itself in Spanish. For the time being this initial translation setup doesn't support the markings statements as translatable strings, once the UX is evolved in later PRs that can be opened up.
• enables the Languages locale drop down menu at the top of the page (pending)
• sets up frontend logic to allow for language selection in dropdown to load appropriate language files from .po/.mo files and output an appropriately translated page. (pending)

Technical details

wpcli i18n make-pot . languages/vocabulary-theme.pot --domain=chooser

Tests

Screenshots

Checklist

• I have read and understood the Developer Certificate of Origin (DCO), below, which covers the contents of this pull request (PR).
• My pull request doesn't include code or content generated with AI (also see Avoiding generative AI development tools — Creative Commons Open Source).
• My pull request has a descriptive title (not a vague title like Update index.md).
• My pull request targets the default branch of the repository (main or master).
• My commit messages follow best practices.
• My code follows the established code style of the repository.
• I added or updated unit tests and/or test scripts for the changes I made (if applicable).
• I added or updated documentation (if applicable).
• I tried running the project locally and verified that there are no
  visible errors.

Developer Certificate of Origin

For the purposes of this DCO, "license" is equivalent to "license or public domain dedication," and "open source license" is equivalent to "open content license or public domain dedication."

Developer Certificate of Origin

Developer Certificate of Origin
Version 1.1

Copyright (C) 2004, 2006 The Linux Foundation and its contributors.
1 Letterman Drive
Suite D4700
San Francisco, CA, 94129

Everyone is permitted to copy and distribute verbatim copies of this
license document, but changing it is not allowed.


Developer's Certificate of Origin 1.1

By making a contribution to this project, I certify that:

(a) The contribution was created in whole or in part by me and I
    have the right to submit it under the open source license
    indicated in the file; or

(b) The contribution is based upon previous work that, to the best
    of my knowledge, is covered under an appropriate open source
    license and I have the right under that license to submit that
    work with modifications, whether created in whole or in part
    by me, under the same open source license (unless I am
    permitted to submit under a different license), as indicated
    in the file; or

(c) The contribution was provided directly to me by some other
    person who certified (a), (b) or (c) and I have not modified
    it.

(d) I understand and agree that this project and the contribution
    are public and that a record of the contribution (including all
    personal information I submit with it, including my sign-off) is
    maintained indefinitely and may be redistributed consistent with
    this project or the open source license(s) involved.