Add Stylelint

... with rules that order declarations, so that any future changes are
devoid of arbitrary reorganisation, instead focused on meaningful change

Per [this client project commit][1], `stylelint-selector bem-pattern` is
added and `selector-class-pattern` is turned off as by default Stylelint
(or the standard rules) require strictly kebab case class names

[1]: ministryofjustice/hmpps-accredited-programmes-ui@025ed66

.stylelintrc.json

@@ -0,0 +1,10 @@
+{
+  "extends": ["stylelint-config-standard-scss", "stylelint-config-clean-order"],
+  "plugins": ["stylelint-selector-bem-pattern"],
+  "rules": {
+    "plugin/selector-bem-pattern": {
+      "preset": "bem"
+    },
+    "selector-class-pattern": null
+  }
+}