chore: Add widget-lib and publish to NPM

[anxolin]

Summary

This PR adds the widget library to the monorepo (credits to @shoom3301 for implementing the main widget in https://shoom3301.github.io/cow-widget/)

This PR creates a publishable lib (meaning we can push it to NPM). We will also be able to use it in another monorepo project, which will make development easier.

The library has its own tests (i created tests just for the param to URL mapping (we could add more coverage if desired):

Last but not least, it adds a way to publish this into production, for that read the lib README for instructions.
For that is uses a custom script that will: copy the README, write the version in the package.json, and publish into NPM

To Test

Just run:
nx test widget-lib

To build:
nx build widget-lib, you will see the artifacts in dist/widget-lib

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Name	Status	Preview	Comments	Updated (UTC)
swap-dev	🔄 Building (Inspect)			Jun 22, 2023 1:05pm

[shoom3301]

Amazing example of addding a new lib!

[shoom3301]

I have this error locally.
Actually, we can just remove the declaration from cowswap/src/libs/widget-lib/src/types.ts