refactor: ESM and CJS transpilation

[andy-haynes]

Pre-flight checklist

• I have read the Contributing Guidelines on pull requests.
• Commit messages follow the conventional commits spec
• If this is a code change: I have written unit tests.
• If this is a new API or substantial change: the PR has an accompanying issue (closes #0000) and the maintainers have approved on my working plan.

Motivation

This PR updates the new packages to support ESM and CJS transpilation from the TypeScript source. By supporting ESM modules we remove hurdles for working with new versions of NodeJS and ESM-based frameworks like Vite, addressing longstanding issues for developers.

Worth noting in this PR:

• No bundling has been introduced, the reasoning being that consumers would import modules directly and rely on bundling and/or tree shaking to produce the dependency graph.
• New package.json files now include exports and browser. exports points the consumer to lib/cjs for require imports and lib/esm for native import. browser references lib/cjs and is currently required for near-api-js to build its bundle with browserify.
• JS files in package scope (e.g. tests) are expected to be ESM-compatible, enabling use of import/export and requiring that relative paths to JS modules include .js file extensions.
• Only the modules at lib/esm are tested currently. It may be overkill to also test the CJS output 🤔

Test Plan

This is entirely a packaging change and so only affects consumers, not any specific runtime functionality. The new example-esm and example-vite packages have been added to demonstrate usage with native modules. Local testing has been done by running near-wallet locally after yarn linking the new near-api-js package, and current bundles have been compared to those produced by the changes in this PR.

Related issues/PRs

This is the most directly-relevant one I found at a glance, but the cascading goodness stemming from this change (on top of breaking NAJ into packages) will likely resolve other issues related to polyfills, bundling, and other usage issues.

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Latest commit: 5960b51

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