dev: add linter rule for commit capitalization

Bad:  'fix(abc): Prevent freezes'
Good: 'fix(abc): prevent freezes'

core/cli/ci.el

@@ -46,6 +46,12 @@
                "\\)!?[^ :]*: ")
               "Invalid type")
 
+        (cons (lambda ()
+                (when (re-search-forward "^[^ :]+: " nil t)
+                  (and (looking-at "[A-Z][^-]")
+                       (not (looking-at "\\(SPC\\|TAB\\|ESC\\|LFD\\|DEL\\|RET\\)")))))
+              "Do not capitalize the first word of the subject")
+
         (cons (lambda ()
                 (looking-at "^\\(bump\\|revert\\|release\\|merge\\|module\\)!?([^)]+):"))
               "This commit type's scope goes after the colon, not before")