Add watch role for macOS, implicitly installed on Linux

UnixCLI.yaml

@@ -23,6 +23,7 @@
     - role: tidy
     - role: tree
     - role: yq
+    - role: watch
 
     - role: llvm
     - role: nodejs

roles/watch/tasks/main.yaml

@@ -0,0 +1,6 @@
+---
+- name: install homebrew package
+  when: ansible_os_family == "Darwin"
+  homebrew:
+    name: watch
+    state: latest