docs: Expand section on creating components

CONTRIBUTING.md

@@ -2,11 +2,42 @@
 
 ## Environment setup
 
+Sadly, the setup cannot be automated arbitrarily (say, using a `make init` target).
+Installing `poetry` requires system packages (`python3`, `pip`, `curl`) that cannot be easily installed on the user's behalf in a distribution-independent way.
+Further, inserting `poetry` in one's `$PATH` is best done manually and consciously (environments, user desires etc. differ too much).
+
 1. [Install `poetry`](https://python-poetry.org/docs/master/#installing-with-the-official-installer).
 
    If you're having trouble with version mismatch, check which version the `poetry` installation currently uses in the [CI](https://github.com/alexpovel/ancv/actions).
-2. Run `poetry install` in the root directly (where the `pyproject.toml` is located).
-3. Enter into the created environment with `poetry shell`, alternatively prepend all commands pertaining to the repository with `poetry run`, like `poetry run python -m ancv`.
+2. Run `poetry install` in the root directly (where the [`pyproject.toml`](./pyproject.toml) is located).
+
+   `poetry` will throw an error here if your Python version isn't supported by the project.
+   If that is the case, look into using [`pyenv`](https://github.com/pyenv/pyenv), which will use the version specified in [`.python-version`](.python-version), guaranteeing a version match.
+3. Enter into the created environment with `poetry shell`.
+
+   *Alternatively*, prepend all commands pertaining to the repository with `poetry run`, like `poetry run python -m ancv`.
 4. Set up `git` hooks provided by [`pre-commit`](https://pre-commit.com/#intro) (already installed through `poetry`): `make hooks`.
 
    For this to work, you will have to have `make` installed (Windows alternatives exist).
+
+## Creating components
+
+### Templates
+
+To create a new template, inherit from [`Template`](./ancv/visualization/templates.py) and simply fulfills its interface:
+It needs a [`__rich_console__`](https://rich.readthedocs.io/en/stable/protocol.html#console-render) method yielding all elements that will eventually make up the output document.
+That's it!
+The implementation is entirely up to you.
+You can use [tables](https://rich.readthedocs.io/en/stable/tables.html), [panels](https://rich.readthedocs.io/en/stable/panel.html), [columns](https://rich.readthedocs.io/en/stable/columns.html) and most else [`rich`](https://github.com/Textualize/rich) has on offer.
+
+`mypy` checks (`make typecheck`) will help getting the implementation right.
+However, note that this method cannot (currently) check whether *all sections* were implemented: for example, *Volunteering* could simply have been forgotten, but the code would run all checks would pass.
+Further, lots of manual and visual testing will be necessary.
+
+### Translations
+
+Simply add your translation [here](./ancv/visualization/translations.py).
+
+### Themes
+
+Simply add your theme [here](./ancv/visualization/themes.py).