Add copyright header

ktorm-support-postgresql/src/main/kotlin/org/ktorm/support/postgresql/EarthDistance.kt

@@ -1,3 +1,19 @@
+/*
+ * Copyright 2018-2021 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
 package org.ktorm.support.postgresql
 
 import org.ktorm.expression.ArgumentExpression