adding installer option with asdf (#563)

created a plugin to install tea via asdf - hoping someone else can find it useful.

Co-authored-by: mvaldes <mvaldes.revilla@gmail.com>
Reviewed-on: https://gitea.com/gitea/tea/pulls/563
Co-authored-by: mvaldes14 <mvaldes14@noreply.gitea.com>
Co-committed-by: mvaldes14 <mvaldes14@noreply.gitea.com>

README.md

@@ -94,6 +94,8 @@ There are different ways to get `tea`:
 
 4. Docker (thirdparty): [tgerczei/tea](https://hub.docker.com/r/tgerczei/tea)
 
+5. asdf (thirdparty): [mvaldes14/asdf-tea](https://github.com/mvaldes14/asdf-tea)
+
 ## Compilation
 
 Make sure you have a current go version installed (1.13 or newer).