feat: add support for installing via bpkg

[SidIcarus]

• bpkg
• package.json to be renamed to bpkg.json once this PR goes through

[fidian]

I won't add a package.json file to this repository because that's a well-known file that relates to Node. I've even contributed to the discussion of bpkg/bpkg#17 and explained how a build system could try to run "npm install".

In order for this to get merged, bpkg/bpkg#18 needs to get merged and this PR has to get updated to use the new filename.