(build) Externalize apollo and graphql libraries

[Austio]

This PR externalizes the peer dependencies in vue-apollo in order to reduce the bundle size of vue-apollo in the default umd build. Without this, all of those libraries are being included and compiled in a way that is not tree-shakable, which causes the bundle size to be quite large.

Closes #660

Library	Before	After WithExternals
esm	133k	57k
min	52k	26k
umd	142k	61k

# Current Build
drwxrwxr-x  2 talos talos   4096 Jul  5 11:50 .
drwxrwxr-x 16 talos talos   4096 Aug  7 10:26 ..
-rw-rw-r--  1 talos talos 133190 Aug  7 10:27 vue-apollo.esm.js
-rw-rw-r--  1 talos talos  52935 Aug  7 10:26 vue-apollo.min.js
-rw-rw-r--  1 talos talos 142186 Aug  7 10:27 vue-apollo.umd.js

# With externals
drwxrwxr-x  2 talos talos  4096 Jul  5 11:50 .
drwxrwxr-x 16 talos talos  4096 Aug  7 10:26 ..
-rw-rw-r--  1 talos talos 57047 Aug  7 10:28 vue-apollo.esm.js
-rw-rw-r--  1 talos talos 26922 Aug  7 10:28 vue-apollo.min.js
-rw-rw-r--  1 talos talos 61127 Aug  7 10:28 vue-apollo.umd.js

[Austio]

@Akryum Anything else you are needing to merge this feller in?

[Akryum]

Thanks! 👍