docs: Add gitlint to README

.gitlint

@@ -5,6 +5,6 @@ line-length=72
 [title-trailing-punctuation]
 [title-hard-tab]
 [title-match-regex]
-regex=^(feat|fix|test|release|chore|security):.*$
+regex=^(feat|fix|test|release|chore|security|docs):.*$
 [body-trailing-whitespace]
-[body-first-line-empty]
+[body-first-line-empty]

README.md

@@ -23,6 +23,9 @@ the stanza format of your preferred XMPP library yourself.
 When submitting a PR, please run the linter using `dart analyze` and make sure that all
 tests still pass using `dart test`.
 
+To ensure uniform commit message formatting, please also use `gitlint` to lint your commit
+messages' formatting.
+
 ## License
 
 Licensed under the MIT license.