LibJS: Handle Infinity in Value::to_number()

Author: https://github.com/linusg
Commit: f226746394
Pull-request: https://github.com/SerenityOS/serenity/pull/1757

Libraries/LibJS/Tests/to-number-basic.js

@@ -22,6 +22,12 @@ try {
     // FIXME: returns NaN
     // assert(+"1.23" === 1.23)
     // assert(-"1.23" === -1.23)
+    assert(+"Infinity" === Infinity);
+    assert(+"+Infinity" === Infinity);
+    assert(+"-Infinity" === -Infinity);
+    assert(-"Infinity" === -Infinity);
+    assert(-"+Infinity" === -Infinity);
+    assert(-"-Infinity" === Infinity);
 
     assert(isNaN(+undefined));
     assert(isNaN(-undefined));