ci(commitlint): addition of commit message linter (#695)

Adds commitlint to check the commit message style against agreed
conventional commits configuration.

Changes script argument values to always use linter names (e.g.
shellcheck).

Changes argument handling to allow only one checking action that can now
accept further optional arguments.

.commitlintrc.yaml

@@ -0,0 +1,21 @@
+rules:
+  body-case: [2, always, sentence-case]
+  body-full-stop: [2, always]
+  body-leading-blank: [2, always]
+  body-max-line-length: [2, always, 72]
+  footer-leading-blank: [2, always]
+  footer-max-line-length: [2, always, 72]
+  header-max-length: [2, always, 72]
+  scope-case: [2, always, lower-case]
+  subject-case:
+    - 2
+    - never
+    - [pascal-case, sentence-case, start-case, upper-case]
+  subject-empty: [2, never]
+  subject-full-stop: [2, never, "."]
+  type-case: [2, always, lower-case]
+  type-empty: [2, never]
+  type-enum:
+    - 2
+    - always
+    - [build, chore, ci, docs, feat, fix, perf, refactor, style, test]