add kiss radio env to most of the variants

variants/station_g2/platformio.ini

@@ -238,3 +238,8 @@ build_src_filter = ${Station_G2.build_src_filter}
 lib_deps =
   ${Station_G2.lib_deps}
   densaugeo/base64 @ ~1.4.0
+
+[env:Station_G2_kiss_modem]
+extends = Station_G2
+build_src_filter = ${Station_G2.build_src_filter}
+  +<../examples/kiss_modem/>