Lua scripts can detect EdgeTX via getVersion

Add a sixth parameter to getVersion so that scripts 
can detect whether running on EdgeTX or OpenTX. 

i.e. `local ver, radio, maj, minor, rev, osname = getVersion()`

radio/src/lua/api_general.cpp

@@ -99,7 +99,16 @@ If running in simulator the "-simu" is added
  * (number) minor version (ie 1 if version 2.1.5)
  * (number) revision number (ie 5 if version 2.1.5)
 
-@status current Introduced in 2.0.0, expanded in 2.1.7, radio type strings changed in 2.2.0
+@retval multiple (available since 2.1.7) returns 6 values:
+ * (string) OpenTX version (ie "2.1.5")
+ * (string) radio type: `x12s`, `x10`, `x9e`, `x9d+`, `x9d` or `x7`.
+If running in simulator the "-simu" is added
+ * (number) major version (ie 2 if version 2.1.5)
+ * (number) minor version (ie 1 if version 2.1.5)
+ * (number) revision number (ie 5 if version 2.1.5)
+ * (string) OS name ( i.e. EdgeTX or nil if OpenTX)
+
+@status current Introduced in 2.0.0, expanded in 2.1.7, radio type strings changed in 2.2.0, os name added in EdgeTX 2.4.0
 
 ### Example
 
@@ -107,12 +116,13 @@ This example also runs in OpenTX versions where the function returned only one v
 
 ```lua
 local function run(event)
-  local ver, radio, maj, minor, rev = getVersion()
+  local ver, radio, maj, minor, rev, osname = getVersion()
   print("version: "..ver)
   if radio then print ("radio: "..radio) end
   if maj then print ("maj: "..maj) end
   if minor then print ("minor: "..minor) end
   if rev then print ("rev: "..rev) end
+  if osname then print ("osname: "..osname) end
   return 1
 end
 
@@ -134,7 +144,8 @@ static int luaGetVersion(lua_State * L)
   lua_pushnumber(L, VERSION_MAJOR);
   lua_pushnumber(L, VERSION_MINOR);
   lua_pushnumber(L, VERSION_REVISION);
-  return 5;
+  lua_pushstring(L, "EdgeTX");
+  return 6;
 }
 
 /*luadoc