Initial work on translations / localization

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/3841

Most of the preparation for this was done by Suguru Hirahara (https://github.com/luixxiul).
I've merely reorganized/polished the scripts and instructions in the `i18n/` directory.

While translations can happen even now, more work is necessary to

- make the translation flow better (integrating Weblate), etc.

- restore the Github Actions workflows that Suguru Hirahara had already developed to
  adapt them to our new workflow

i18n/requirements.txt

@@ -0,0 +1,33 @@
+alabaster==1.0.0
+babel==2.16.0
+certifi==2024.12.14
+charset-normalizer==3.4.0
+click==8.1.7
+docutils==0.21.2
+idna==3.10
+imagesize==1.4.1
+Jinja2==3.1.4
+linkify-it-py==2.0.3
+markdown-it-py==3.0.0
+MarkupSafe==3.0.2
+mdit-py-plugins==0.4.2
+mdurl==0.1.2
+myst-parser==4.0.0
+packaging==24.2
+Pygments==2.18.0
+PyYAML==6.0.2
+requests==2.32.3
+setuptools==75.6.0
+snowballstemmer==2.2.0
+Sphinx==8.1.3
+sphinx-intl==2.3.1
+sphinx-markdown-builder==0.6.7
+sphinxcontrib-applehelp==2.0.0
+sphinxcontrib-devhelp==2.0.0
+sphinxcontrib-htmlhelp==2.1.0
+sphinxcontrib-jsmath==1.0.1
+sphinxcontrib-qthelp==2.0.0
+sphinxcontrib-serializinghtml==2.0.0
+tabulate==0.9.0
+uc-micro-py==1.0.3
+urllib3==2.2.3