Updating docs to include install for alpine and node 12

[sstewart199]

Installing pouchdb-server on Alpine Linux based images

You need the following packages:

• build-base
• python

apk --no-cache add --virtual builds-deps build-base python

We recommend using no-cache and virtual, in order to keep the resulting container size same.

Alpine linux based images use musl libc instead of the standard glibc and thus are not compatible with compiled binaries. node-pre-gyp currently does not test the pre-compiled binaries to be ABI-compatible and thus you may see segfaults. We are working to resolve this issue.

As a workaround, In alpine based images, force recompiling the leveldown native addon after a npm install with this command: npm rebuild leveldown --build-from-source.

RUN apk --no-cache add --virtual builds-deps build-base python
RUN yarn --production && npm rebuild leveldown --build-from-source
CMD node node_modules/pouchdb-server -p 5432