fix: only check value of type attribute in prefer-button rule

The prefer-button rule should detect <input> elements of button-like
types. Searching all attribute values for these types, e.g. "submit",
yields false positives if this string in other places.

We now only check the value of the "type" attribute to prevent false
positives with this rule.

src/rules/prefer-button.spec.ts

@@ -80,6 +80,14 @@ describe("rule prefer-button", () => {
 			);
 		});
 
+		it("should not report error when using submit keyword in other attributes", () => {
+			expect.assertions(1);
+			const report = htmlvalidate.validateString(
+				'<input type="hidden" name="action" value="submit">'
+			);
+			expect(report).toBeValid();
+		});
+
 		it("smoketest", () => {
 			expect.assertions(1);
 			const report = htmlvalidate.validateFile("test-files/rules/prefer-button.html");

src/rules/prefer-button.ts

@@ -82,6 +82,11 @@ export default class PreferButton extends Rule<RuleContext, RuleOptions> {
 				return;
 			}
 
+			/* only handle type attribute */
+			if (event.key !== "type") {
+				return;
+			}
+
 			/* sanity check: handle missing, boolean and dynamic attributes */
 			if (!event.value || event.value instanceof DynamicValue) {
 				return;