Refresh export structure in package.json

[Acconut]

Currently, tus-js-client uses the outdated main, module, and browser fields to indicate what files users should access when the package is imported:

tus-js-client/package.json

Lines 5 to 13 in b147b53

	"main": "lib.es5/node/index.js",
	"module": "lib.esm/node/index.js",
	"files": ["lib/**/*", "lib.es5/**/*", "lib.esm/**/*", "dist/**/*", "lib/index.d.ts"],
	"browser": {
	"./lib.es5/node/index.js": "./lib.es5/browser/index.js",
	"./lib.esm/node/index.js": "./lib.esm/browser/index.js",
	"./lib/node/index.js": "./lib/browser/index.js"
	},
	"types": "./lib/index.d.ts",

After #683 is completed, we should upgrade this to more recent syntax that also incorporates the exports syntax. Resources:

• https://webpack.js.org/guides/package-exports
• https://nodejs.org/api/packages.html#package-entry-points

The benefit is that tool can either resolve to the CommonJS or ESM variants of tus-js-client. We can also consider exporting different types for browser and Node.js environments, as well as making environment-specific imports possible (e.g. import ... from 'tus-js-client/react-native/fileReader'). Resources:

• https://arethetypeswrong.github.io/?p=tus-js-client%404.1.0 (run locally via npx @arethetypeswrong/cli --pack .)
• https://publint.dev/[email protected] (run locally via npx publint)
• https://github.com/frehner/modern-guide-to-packaging-js-library