[Keyboard] Added Atreus Pro Micro variant (#8059)

* new alternative controller.

* following suggestions at qmk's 8059.

* forgot to replace some underscores and keycodes.

* following drashna's suggestions at qmk's 8059.

* following zvecr's suggestion in qmk's 8059.

* following noroadsleft's suggestion at qmk's 8059.

keyboards/atreus/promicro/promicro.h

@@ -0,0 +1,17 @@
+/* Copyright 2019
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once