fix: Dockerfile to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-ALPINE318-OPENSSL-7413525
- https://snyk.io/vuln/SNYK-ALPINE318-OPENSSL-7413525
- https://snyk.io/vuln/SNYK-ALPINE318-OPENSSL-7413536
- https://snyk.io/vuln/SNYK-ALPINE318-OPENSSL-7413536

Dockerfile

@@ -47,13 +47,13 @@ RUN go install github.com/yaegashi/muslstack@latest && \
 
 # ---
 
-FROM alpine:3.18
+FROM alpine:3
 
 # renew global args from above & pin any dependency versions
 ARG HUGO_VERSION
 # https://github.com/jgm/pandoc/releases
 # renovate: datasource=github-releases depName=jgm/pandoc
-ARG PANDOC_VERSION=3.6.2
+ARG PANDOC_VERSION=3.1.13
 # https://github.com/sass/dart-sass-embedded/releases
 # renovate: datasource=github-releases depName=sass/dart-sass-embedded
 ARG DART_SASS_VERSION=1.62.1