modernize build test and lint

[chris-armstrong]

This is a PR to modernize the build and test infrastructure, including:

• using preconstruct to generate ESM and commonjs compatible exports for bundling
• removing the use of gulp and replacing with npm scripts
• upgrading packages to address security warnings

[whitlockjc]

First off, thanks a ton for taking this on. I'll review this more in depth ASAP.

[whitlockjc]

It looks like the majority of this code was to move to using export and import keywords, and a lot of other changes were a result of this. I'm fine with evolution, but I'd really like to understand why and also to make sure we're making only necessary changes.

[chris-armstrong]

I should note that I'm no longer depending on these changes to make further additions, so I won't be chasing these up, but they may be useful to anyone consuming the library or submitting PRs.

[whitlockjc]

@chris-armstrong Thanks again for doing this, and if you're still willing to help me get this ready to merge, I'd love to use it. I know you said you don't depend on this anymore but I think the changes you're suggesting could be welcome. Where does this PR stand in your opinion? Also, do you mind updating CONTRIBUTING.md to reflect the new build/release process?

[chris-armstrong]

I don't have anything I want to add to this PR, but because it's been a couple of months, and I'm not using the changes, I think best next step is to verify it hasn't regressed for downstream consumers of the module.

I'd say the next steps is to:

• resolve outstanding merge conflicts
• build and release as an alpha version on npm so that it can be upgraded in downstream projects to test compatibility
• update CONTRIBUTING.md to reflect new build process (npm run build)