add kiss radio env to most of the variants

variants/thinknode_m2/platformio.ini

@@ -209,3 +209,10 @@ build_src_filter = ${ThinkNode_M2.build_src_filter}
 lib_deps =
   ${ThinkNode_M2.lib_deps}
   densaugeo/base64 @ ~1.4.0
+
+[env:ThinkNode_M2_kiss_modem]
+extends = ThinkNode_M2
+build_flags = ${ThinkNode_M2.build_flags}
+  -UPIN_BUZZER
+build_src_filter = ${ThinkNode_M2.build_src_filter}
+  +<../examples/kiss_modem/>