Merge branch 'renovate/docker.io-library-nginx-1.x' into 'master'

Update docker.io/library/nginx Docker tag to v1.21.3

See merge request !50

_docker/Dockerfile

-FROM docker.io/library/nginx:1.21.1-alpine
+FROM docker.io/library/nginx:1.21.3-alpine
 
 COPY ./public/ /usr/share/nginx/html/