docs: add info about decision to use github

docs/decisions/0005-github.md

@@ -0,0 +1,47 @@
+# Use Github as both our code repository & CI/CD
+
+## Context and Problem Statement
+
+We need somewhere to
+
+- Store our code to work on it collaboratively.
+- Raise issues and manage documentation around the code.
+- Track development via roadmaps and task trackers.
+
+We also need a pipeline runner (CI/CD):
+
+- Create build artifacts for deployment.
+- Run automated testing.
+- Deploy our code into various development environments.
+
+## Considered Options
+
+- Github
+- Gitlab
+- Codeberg
+- Bitbucket
+
+## Decision Outcome
+
+Github was originally chosen as it provided many benefits for free, over the
+competition.
+
+Cost and simplicity are key factors for us, being a small NGO that receives
+project specific funding.
+
+Since the decision was taken, Github was acquired by Microsoft and has
+some practices that we do not agree with (license violations for Copilot,
+amongst others).
+
+Reluctantly, we are stuck with Github due to the migration effort that would
+be required.
+
+### Consequences
+
+- Good, because free to use, including uncapped CI/CD usage as an NGO.
+- Good, has the most visibility and reach of all other platforms.
+- Bad, because as an organization it undertakes many practices we do not agree with.
+- Bad, the more we use Github workflows (propriatary), the further we are
+  vendor-locked.
+- Bad, because it would be difficult to migrate all of the accumulated issues,
+  milestones, project boards, subissues, etc.

docs/decisions/0006-slack.md

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+# Use Slack to engage with our community members

mkdocs.yml

@@ -143,6 +143,8 @@ nav:
       - Tech Decisions:
           - React: decisions/0003-react.md
           - Python: decisions/0004-python.md
+          - Github: decisions/0005-github.md
+          - Slack: decisions/0006-slack.md
           - API Documentation: decisions/0002-mkdocs.md
           - Technical Diagrams: decisions/0001-draw-io.md
   - DevOps: