Add note about Gitea version (#11)

Fixes #8 by clarifying the requirements.

Author: jonasfranz

README.md

@@ -6,11 +6,13 @@
 
 Drone plugin to publish files and artifacts to Gitea Release.
 
+**Note: This plugin requires Gitea 1.5 or newer.**
+
 ## Build
 
 Build the binary with the following commands:
 
 ```
 GOOS=linux GOARCH=amd64 CGO_ENABLED=0 go build -a -tags netgo -o release/linux/amd64/drone-gitea-release
 docker build --rm -t plugins/gitea-release .
-```
+```