feat: Add pre-commit hook support

Add pre-commit hook support for flipt validate. This allows users to add
a pre-commit hook that calls validates flipt feature flag configuration
as part of GitOps workflows.

.pre-commit-hooks.yaml

@@ -0,0 +1,15 @@
+- id: flipt-validate
+  name: flipt validate
+  description: Fast linters runner for Go. Runs on all files in the repo. Use this hook if you use pre-commit in CI.
+  entry: flipt validate
+  language: golang
+  types: [yaml]
+  pass_filenames: false
+  files: |
+    (?x)^(
+        .*/features\.yaml|
+        .*/features\.yml|
+        .*?/.*\.features.yaml|
+        .*?/.*\.features.yml
+    )$
+