fix(is-ignored): ignore merge tag commit messages (#2920)

Merging a tag in another branch can lead to conflicts.
In this case, the default Git commit message after resolving the conflicts will be like:
   `Merge tag 'x.y.z'`

Currently, this commit message format is being considered as an error.
So I updated the wildcards to get a consistent behavior between branch and tag merge:
 - `Merge branch 'a branch'`
 - `Merge branch 'a tag'`

Author: gaetanmaisse

@commitlint/is-ignored/src/defaults.ts

@@ -18,6 +18,7 @@ export const wildcards: Matcher[] = [
 	test(
 		/^((Merge pull request)|(Merge (.*?) into (.*?)|(Merge branch (.*?)))(?:\r?\n)*$)/m
 	),
+	test(/^(Merge tag (.*?))(?:\r?\n)*$/m),
 	test(/^(R|r)evert (.*)/),
 	test(/^(fixup|squash)!/),
 	isSemver,

@commitlint/is-ignored/src/is-ignored.test.ts

@@ -70,6 +70,26 @@ test('should return true for branch merges with newline characters and more char
 	);
 });
 
+test('should return true for tag merges', () => {
+	expect(isIgnored("Merge tag '1.1.1'")).toBe(true);
+	expect(isIgnored("Merge tag 'a tag'")).toBe(true);
+});
+
+test('should return true for tag merges with newline characters', () => {
+	expect(isIgnored("Merge tag '1.1.1'\n")).toBe(true);
+	expect(isIgnored("Merge tag '1.1.1'\r\n")).toBe(true);
+});
+
+test('should return true for tag merges with multiple newline characters', () => {
+	expect(isIgnored("Merge tag '1.1.1'\n\n\n")).toBe(true);
+	expect(isIgnored("Merge tag '1.1.1'\r\n\r\n\r\n")).toBe(true);
+});
+
+test('should return true for tag merges with newline characters and more characters after it', () => {
+	expect(isIgnored("Merge tag '1.1.1'\n ")).toBe(true);
+	expect(isIgnored("Merge tag '1.1.1'\r\n # some comment")).toBe(true);
+});
+
 test('should return true for revert commits', () => {
 	expect(
 		isIgnored(
@@ -133,6 +153,10 @@ test('should return false for commits containing, but not starting, with merge b
 	expect(isIgnored('foo bar Merge branch xxx')).toBe(false);
 });
 
+test('should return false for commits containing, but not starting, with merge tag', () => {
+	expect(isIgnored("foo bar Merge tag '1.1.1'")).toBe(false);
+});
+
 test('should return false for ignored message if defaults is false', () => {
 	expect(
 		isIgnored('Auto-merged develop into master', {