Gradle: use the assignment operator in the maven repo section

Author: carlosame

README.md

@@ -35,7 +35,7 @@ your build file:
 ```groovy
 repositories {
     maven {
-        url "https://css4j.github.io/maven/"
+        url = "https://css4j.github.io/maven/"
         mavenContent {
             releasesOnly()
         }

build.gradle

@@ -67,7 +67,7 @@ repositories {
 		url = uri('https://repo.maven.apache.org/maven2/')
 	}
 	maven {
-		url "https://css4j.github.io/maven/"
+		url = "https://css4j.github.io/maven/"
 		mavenContent {
 			releasesOnly()
 		}