Add SourceHut build file

For now it only attempts to install the Python requirements using
pipenv. Later it will run tests with pytest.

.build.yml

@@ -0,0 +1,11 @@
+image: archlinux
+packages:
+  - python-pipenv
+sources:
+  - https://git.sr.ht/~alanorth/csv-metadata-quality
+tasks:
+  - setup: |
+      pipenv install
+environment:
+  PIPENV_NOSPIN: 'True'
+  PIPENV_HIDE_EMOJIS: 'True'