fix(build): bump dnsmasq to 2.91-r0 (#14)

The proposed change updates the `dnsmasq` version in the Dockerfile.

Specifically, the line:

```diff
-RUN apk --no-cache add dnsmasq=2.90-r3
+RUN apk --no-cache add dnsmasq=2.91-r0
```

is modified.  This line installs the `dnsmasq` package using Alpine Package Keeper (apk). The change updates the version of `dnsmasq` from `2.90-r3` to `2.91-r0`. This likely incorporates bug fixes, security updates, or new features present in the newer version.

Reviewed-on: #14

Dockerfile

@@ -9,7 +9,7 @@ RUN apk add --no-cache curl && \
     chmod +x /usr/local/bin/webproc
 
 FROM build AS dnsmasq
-RUN apk --no-cache add dnsmasq=2.90-r3
+RUN apk --no-cache add dnsmasq=2.91-r0
 COPY --from=webproc /usr/local/bin/webproc /usr/local/bin/webproc
 ENTRYPOINT ["webproc","-o","restart","-c","/etc/dnsmasq.conf","-c","/etc/hosts","-c","/etc/resolv.conf","--","dnsmasq","-k","--log-facility=-"]
 EXPOSE 53/udp 8080/tcp