[pre-commit] Add yamllint hook

Add pre-commit check linting .pre-commit-config.yaml using yamllint.

[1] https://github.com/adrienverge/yamllint

.pre-commit-config.yaml

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 733f00a..66cbc11 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -101,6 +101,13 @@
         args: [--trust-plugins]
         files: '^gdb/testsuite/.*\.(exp|tcl)$'
 
+  # Yaml hooks.
+  - repo: https://github.com/adrienverge/yamllint.git
+    rev: v1.38.0
+    hooks:
+      - id: yamllint
+        files: '^\.pre-commit-config.yaml$'
+
   # Local hooks.
   - repo: local
     hooks: