Fix build for more recent releases of Node.js

[amotl]

Hi there,

this adds compatibility for Node.js >11.15, see #101, #102 and #109.

With kind regards,
Andreas.

Build instructions

When using Node.js >11.15, these commands might work already.

# Install dependencies.
npx yarn install

# Run build.
npx yarn build

When Yarn is not installed (YMMV), this command might help:

# Install yarn globally.
npm install yarn -g

[daldoyle]

Hi there,

Thanks very much for this PR and apologies for the big delay in getting back to you. We've been internally swapping over various repos to using "yarn" instead, and we ended up semi using this PR as the basis for that. I'm going to close this out and merge in the other one since it finalizes some other changes as well but wanted to make sure I left a note here saying thanks for the ideas.