Restructure pipelines and badges

- Seperate test pipeline into E2E, integration and unit test pipelines.
- Improve documenetation for pipelines (ci-cd.md).
- Introduce naming convention for worklow files and names.
- Center badges with multiple files on README file.

docs/ci-cd.md

@@ -0,0 +1,19 @@
+# Pipelines
+
+Pipelines are found under [`.github/workflows`](./../.github/workflows).
+
+## Pipeline types
+
+They are categorized based on their type:
+
+- `tests`: Different types of tests to verify functionality.
+- `checks`: Other controls such as vulnerability scans or styling checks.
+- `release`: Pipelines used for release of deployment such as building and testing.
+
+## Naming conventions
+
+Pipeline files are named using: **`<type>.<name>.yaml`**.
+
+**`type`**: Sub-folders do not work for GitHub workflows so that's why `<type>.` prefix is used. See also [pipeline types](#pipeline-types).
+
+**`name`**: Pipeline themselves are named using kebab case. It allows for easier URL references for their status badges. E.g. file name `tests.unit.yaml`, pipeline name: `name: unit-tests`