fix: Dockerfile to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-ALPINE318-OPENSSL-8235200
- https://snyk.io/vuln/SNYK-ALPINE318-OPENSSL-8235200

.github/workflows/build.yml

@@ -24,7 +24,7 @@ jobs:
     if: "!contains(github.event.head_commit.message, '[skip ci]')"
     steps:
       - name: Checkout
-        uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4
+        uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11 # v4
         with:
           fetch-depth: 0
 

Dockerfile

@@ -47,7 +47,7 @@ RUN go install github.com/yaegashi/muslstack@latest && \
 
 # ---
 
-FROM alpine:3.18
+FROM alpine:3.21.0
 
 # renew global args from above & pin any dependency versions
 ARG HUGO_VERSION