site: use gcloud CLI to build Docker image

[Conduitry]

A few changes here:

• the Makefile now uses gcloud builds submit to build the image (remotely) rather than locally with Docker and then pushing it
• there's now a .dockerignore which whitelists only the files needed by the Sapper app
• there's a .gcloudignore that just points to that .dockerignore (the reason for having both is so that the old docker build will continue to work nicely if so desired)
• the Dockerfile now only copies the package[-lock].json files to the first container before installing deps, and then copies the installed packages and every (non-ignored) file in the directory to the second and final container (this is to avoid a little bit of extra copying of the app itself to the first container, which isn't really necessary)
• installation of npm packages is now done with npm ci

[codecov-io]

Codecov Report

Merging #2479 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #2479   +/-   ##
=======================================
  Coverage   91.83%   91.83%           
=======================================
  Files           1        1           
  Lines          49       49           
=======================================
  Hits           45       45           
  Misses          4        4

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[Conduitry]

The upshot of all of this is:

• docker is no longer required to be installed locally to deploy
• stuff in e.g. __sapper__/dev is no longer getting copied into the image - __sapper__/build is the only thing in __sapper__ that's included now

[lukeed]

Could we make it this instead? I think it has same result

**
!/Dockerfile
!/package.json
!/package-lock.json
!/__sapper__/build/**
!/content
!/static

Ignore absolutely everything except these...

[lukeed]

Built locally and it was the same

[Conduitry]

That doesn't work

Creating temporary tarball archive of 3 file(s) totalling 235.3 KiB before compression. - only package.json, package-lock.json, and Dockerfile are included.

It's got something to do with not being able to include __sapper__/build/... if all of __sapper__ was already excluded.

When I was playing with GCR for the first time a couple of weeks ago, I spent a while wading through SO answers about gitignore trying to get this to work. I'm pretty sure there's not a tidier way to specifically include these files.

[lukeed]

Ah, right! It works for docker alone, but gcloudignore is a bit different.

[Rich-Harris]

this is wonderful and i just about understand it