fix(rules): better error message for `attr-delimiter`

src/rules/__snapshots__/attr-delimiter.spec.ts.snap

@@ -2,7 +2,7 @@
 
 exports[`rule attr-delimiter should contain documentation 1`] = `
 Object {
-  "description": "Attribute value should be separated by ",
+  "description": "Attribute value must not be separated by whitespace.",
   "url": "https://html-validate.org/rules/attr-delimiter.html",
 }
 `;

src/rules/attr-delimiter.ts

@@ -12,7 +12,7 @@ function isRelevant(event: TokenEvent): boolean {
 export default class AttrDelimiter extends Rule {
 	public documentation(): RuleDocumentation {
 		return {
-			description: `Attribute value should be separated by `,
+			description: `Attribute value must not be separated by whitespace.`,
 			url: ruleDocumentationUrl(__filename),
 		};
 	}