[Keyboard] Add pico as a new keyboard (#7419)

* Add keyboards/ pico as a new keyboad.

* Add keyboards/pico rev1.

* Add keyboards/pico keymaps/default.

* Add keyboards/pico keymaps/jis.

* Remove unneeded code of rules.mk.

* Revert rules.mk and remove some comments.

keyboards/pico/keymaps/jis/config.h

@@ -0,0 +1,18 @@
+/*
+Copyright 2019 Kumao Kobo <kumaokobo@gmail.com>
+
+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