fix: Dockerfile to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-ALPINE318-OPENSSL-5776808
- https://snyk.io/vuln/SNYK-ALPINE318-OPENSSL-5776808
- https://snyk.io/vuln/SNYK-ALPINE318-OPENSSL-5788370
- https://snyk.io/vuln/SNYK-ALPINE318-OPENSSL-5788370
- https://snyk.io/vuln/SNYK-ALPINE318-OPENSSL-5821142

Dockerfile

@@ -4,7 +4,7 @@ COPY . /app
 WORKDIR /app
 RUN make build
 
-FROM alpine:latest
+FROM alpine:3.18.3
 
 COPY --from=builder /app/bin/chia-exporter /chia-exporter
 CMD ["/chia-exporter", "serve"]