Merge pull request #2432 from recrof/kiss-radio-everywhere

kiss radio: added stm32 support + envs in platformio.ini

variants/rak11310/platformio.ini

@@ -132,3 +132,8 @@ build_src_filter = ${rak11310.build_src_filter}
   +<../examples/simple_secure_chat/main.cpp>
 lib_deps = ${rak11310.lib_deps}
   densaugeo/base64 @ ~1.4.0
+
+[env:RAK_11310_kiss_modem]
+extends = rak11310
+build_src_filter = ${rak11310.build_src_filter}
+  +<../examples/kiss_modem/>