add kiss radio env to most of the variants

variants/heltec_v4/platformio.ini

@@ -429,3 +429,8 @@ build_src_filter = ${heltec_v4_tft.build_src_filter}
 lib_deps =
   ${heltec_v4_tft.lib_deps}
   ${esp32_ota.lib_deps}
+
+[env:heltec_v4_kiss_modem]
+extends = Heltec_lora32_v4
+build_src_filter = ${Heltec_lora32_v4.build_src_filter}
+  +<../examples/kiss_modem/>