Add tests and publish repository metadata for MIL-003

Add 19 pytest tests covering the report, resource check, coin
processing, refunds, change, profit, make_coffee and the main loop.
Add a tests package and put the project root on the pytest path.
Doxygen output is clean. The repository description and topics were set
on the git host.

Closes #13
Closes #14
Closes #15
Closes #16
Closes #17

Task: MIL-003#1
Task: MIL-003#2
Task: MIL-003#3
Task: MIL-003#4
Task: MIL-003#5

tests/conftest.py

@@ -0,0 +1,25 @@
+"""!
+@file conftest.py
+@brief Shared pytest helpers.
+"""
+
+from collections.abc import Callable, Iterable
+
+import pytest
+
+ScriptInput = Callable[[Iterable[str]], None]
+
+
+@pytest.fixture
+def script_input(monkeypatch: pytest.MonkeyPatch) -> ScriptInput:
+    """!
+    @brief Provide a function that feeds the given answers to `input`.
+    @param monkeypatch pytest's monkeypatch fixture.
+    @return A function taking the answers in the order they are asked.
+    """
+
+    def feed(answers: Iterable[str]) -> None:
+        remaining = iter(answers)
+        monkeypatch.setattr("builtins.input", lambda _prompt: next(remaining))
+
+    return feed