Use ResolveReference instead of path.Join (#4073)

Signed-off-by: Jonas Franz <info@jonasfranz.software>

modules/markup/html_test.go

@@ -83,6 +83,8 @@ func TestURLJoin(t *testing.T) {
 			"a", "b/c/"),
 		newTest("a/b/d",
 			"a/", "b/c/", "/../d/"),
+		newTest("https://try.gitea.io/a/b/c#d",
+			"https://try.gitea.io", "a/b", "c#d"),
 	} {
 		assert.Equal(t, test.Expected, URLJoin(test.Base, test.Elements...))
 	}