That truck is unicode character U+1F69A.
https://en.wikipedia.org/wiki/Transport_and_Map_Symbols
https://en.wikipedia.org/wiki/Unicode
someone with more knowledge of unicode and emojis (etc) than me may be able to offer different/better advice, but I don't think you can do exactly what you want to do. Programs/devices support certain pre-configured character/symbol sets. Even if it was possible for you to define your own new custom character on your own device, no one would be able to see your character unless they too loaded that custom character definition into their device/program.