Merge branch 'renovate/alpine-3.x' into 'master'

Update alpine Docker tag to v3.21.0

See merge request !31

Dockerfile

@@ -4,7 +4,7 @@ COPY go.mod go.sum ./
 RUN go mod download
 COPY *.go ./
 RUN CGO_ENABLED=0 GOOS=linux go build -o /rss2gotify
-FROM alpine:3.20.3
+FROM alpine:3.21.0
 RUN apk add --no-cache ca-certificates
 COPY --from=build /rss2gotify /rss2gotify
 ENTRYPOINT ["/rss2gotify"]
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