add kiss radio env to most of the variants

variants/lilygo_techo/platformio.ini

@@ -126,3 +126,8 @@ build_src_filter = ${LilyGo_T-Echo.build_src_filter}
 lib_deps =
   ${LilyGo_T-Echo.lib_deps}
   densaugeo/base64 @ ~1.4.0
+
+[env:LilyGo_T-Echo_kiss_modem]
+extends = LilyGo_T-Echo
+build_src_filter = ${LilyGo_T-Echo.build_src_filter}
+  +<../examples/kiss_modem/>