[NayNay] Improving build system for SDK

[rh0delta]

Description

Users were unable to import the individual methods from the subfolders within the package dist. This update provides the ability to perform these individual imports, rather than having to import in the full package.

Changes

• updated package json with exports field to be able to import subfolders from the package
• added a new entry to both npmingnore and gitignore, this was the folder i used for testing the changes to package.json

GitHub Issue or Linear Task

How Has This Been Tested?

1. created new npm project
2. linked @entropyxyz/sdk to new project
3. imported in new package and logged contents Code: import Entropy from '@entropyxyz/sdk'; import { getWallet } from '@entropyxyz/sdk/keys'; import * as crypto from '@entropyxyz/sdk/cypto-utils'; import * as utils from '@entropyxyz/sdk/gen-utils'; console.log(Entropy); console.log(getWallet); console.log(crypto); console.log(utils); Result: [class Entropy] [AsyncFunction (anonymous)] [Module: null prototype] { crypto: {}, cryptoIsLoaded: Promise { <pending> }, loadCryptoLib: [AsyncFunction: loadCryptoLib] } [Module: null prototype] { buf2hex: [Function: buf2hex], hex2buf: [Function: hex2buf], isValidSubstrateAddress: [Function: isValidSubstrateAddress], sendHttpPost: [AsyncFunction: sendHttpPost], stripHexPrefix: [Function: stripHexPrefix], typeofthing: [Function: typeofthing] }