docs: adding FEATURE-GATES.md file

Basic instructions on how to use feature gates.

Signed-off-by: Beraldo Leal <[email protected]>

Author: beraldoleal

docs/FEATURE-GATES.md

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+# Feature Gates
+
+Feature Gates in the Openshift Sandboxed Containers operator allow
+administrators to enable or disable specific features. These features are
+controlled through the `FeatureGates` struct in the operator's configuration,
+providing a flexible approach to testing new features and managing the rollout
+of stable functionalities.
+
+## Maturity Levels
+
+Our feature gates adhere to simplified lifecycle stages inspired by Kubernetes:
+
+- **DevPreview**:
+  - Disabled by default.
+  - May contain bugs; enabling the feature could expose these bugs.
+  - No long-term support guarantees.
+
+- **TechPreview**:
+  - Usually disabled by default.
+  - Support for the feature will not be dropped, but details may change.
+  - Recommended for non-business-critical usage due to potential for changes.
+
+- **GA (General Availability)**:
+  - Enabled by default
+  - Well-tested and considered safe.
+  - Stable features will be maintained in future software releases.
+
+## Disclaimer
+
+> [!WARNING]
+> Remember, the availability and default state of each feature may change between
+> releases as features progress through their maturity levels. Always refer to
+> the latest documentation for up-to-date information on feature support and
+> configuration.
+
+## Configuring Feature Gates
+
+Feature gates can be enabled or disabled by editing the `osc-feature-gates` ConfigMap
+resource. Each feature gate allows you to toggle specific functionalities,
+adjusting your cluster's behavior as needed.
+
+### Enabling and disabling features
+
+To enable a feature, you modify your `ConfigMap` object like so:
+
+```yaml
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: osc-feature-gates
+  namespace: openshift-sandboxed-containers-operator
+data:
+  timeTravel: "true"
+  quantumEntanglementSync: "false"
+  autoHealingWithAI: "true"
+```
+
+In this example, `timeTravel` is explicitly enabled, while
+`quantumEntanglementSync` is disabled, and `autoHealingWithAI` is enabled,
+showcasing how to manage the state of each feature individually. Regardless the
+default values they have.