create custom docker image for fargo actions

.github/test_image/Dockerfile

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+FROM ghcr.io/gleam-lang/gleam:v1.15.2-erlang
+
+RUN apt-get update && apt-get install -y nodejs npm && rm -rf /var/lib/apt/lists/*

.github/test_image/build.sh

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+#!/bin/sh
+
+set -e
+
+export AWS_PROFILE=personal
+export AWS_REGION=eu-central-1
+
+REPO_NAME="gleam-tester-homelabstack"
+
+if ! aws ecr describe-repositories --repository-names "$REPO_NAME" >/dev/null 2>&1; then
+  aws ecr create-repository --repository-name "$REPO_NAME"
+fi
+
+docker buildx build --platform linux/amd64,linux/arm64 -t "853019563312.dkr.ecr.eu-central-1.amazonaws.com/${REPO_NAME}:latest" --push .
+
+echo "Docker image built and pushed to AWS ECR"