Add project scope

[fulldecent]

This artifact is now about 1MB compressed. It is so large that projects are working around it and creating their own slim versions.

Could the scope of this project (what should be included and what should not) please be added to the main README? This will help stop scope creep and set a reasonable project goal that we can all work towards.

[nivida]

The bundle size of web3.js will get improved with de-duplicating of the dependency tree in 1.0 and we will provide new ways to import functionalities from web3.js in the most tree shakable way with 2.0.
But we will definitely add a section to the README to explain the exact scope of this project. Thanks!

[github-actions]

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