Docs: literal compare rule (#2415)

* literal compare rule docs

* Update literal_compare.md

Co-authored-by: Sorin Sbarnea <sorin.sbarnea@gmail.com>

src/ansiblelint/rules/literal_compare.md

@@ -0,0 +1,29 @@
+# literal-compare
+
+This rule checks for literal comparison with the `when` clause.
+Literal comparison, like `when: var == True`,  is unnecessarily complex.
+Use `when: var` to keep your playbooks simple.
+
+## Problematic Code
+
+```yaml
+---
+- name: Example playbook
+  hosts: all
+  tasks:
+    - name: Print environment variable to stdout
+      ansible.builtin.command: echo $MY_ENV_VAR
+      when: ansible_os_family == True # <- Adds complexity to your playbook.
+```
+
+## Correct Code
+
+```yaml
+---
+- name: Example playbook
+  hosts: all
+  tasks:
+    - name: Print environment variable to stdout
+      ansible.builtin.command: echo $MY_ENV_VAR
+      when: ansible_os_family # <- Keeps your playbook simple.
+```