Configuration transposed into environment variables (#82)

Configuration file not required anymore
DIUN_DB env var renamed DIUN_DB_PATH
Only accept duration as timeout value (10 becomes 10s)
Add getting started doc
Enhanced documentation
Add note about test notifications (#79)
Improve configuration management
Fix telegram init
All fields in configuration now camelCased
Improve configuration validation
Update doc
Update FAQ

Co-authored-by: CrazyMax <crazy-max@users.noreply.github.com>

pkg/registry/manifest.go

@@ -48,7 +48,7 @@ func (c *Client) Manifest(image Image) (Manifest, error) {
 	}
 
 	imgTag := imgInspect.Tag
-	if imgTag == "" {
+	if len(imgTag) == 0 {
 		imgTag = image.Tag
 	}