feat(alpine): update to node 14

closes #256
- sharp's issue has been fixed, node 14 doesn't cause segfaults on alpine anymore

4/alpine/Dockerfile

@@ -1,10 +1,7 @@
 # https://docs.ghost.org/faq/node-versions/
 # https://github.com/nodejs/Release (looking for "LTS")
 # https://github.com/TryGhost/Ghost/blob/v4.1.2/package.json#L38
-# TODO: node 14 on alpine 3.13 has an issue with sharp/image resizing
-# see: https://github.com/docker-library/ghost/issues/256
-# sticking to Node 12 until the underlying sharp issue is resolved
-FROM node:12-alpine3.12
+FROM node:14-alpine3.13
 
 # grab su-exec for easy step-down from root
 RUN apk add --no-cache 'su-exec>=0.2'