Unneeded files are being packaged

[rubensworks]

Since the package.json file does not explicitly list the required "files" for npm deployment, many unneeded files are included, which makes the package larger than needed.

Some entries that may be excluded:

• .changeset
• .github
• .eslintrc.js
• rdf-js-tests.ts
• tsconfig.json

[matthieubosquet]

Attempt at fixing this issue: #44.

[matthieubosquet]

Second attempt at fixing this issue: #47.