fix: add buffer

[hugomrdias]

This PR adds buffer as a dependency to avoid relying on bundlers automatic node globals injection.

[feross]

This PR should not have been merged IMO. There are several issues:

1. require('buffer') always uses the Node.js buffer, ignoring the buffer package from npm which is installed in node_modules. To use the npm version, you need to do require('buffer/').

2. We don't actually want to use the npm version when running in Node.js since it's less efficient and compatible than the built-in Buffer.

[hugomrdias]

1. Exactly but if you use bundlers without node builtins injection you get the npm package
2. This package will use node buffer when in node, exactly why I didn't use require('buffer/')

So this works exactly the same way as before plus supports bundlers without injection.

[hugomrdias]

@feross any chance i can convince you to reimplement this ?
This PR is part of a larger endeavour to remove node globals and built ins from ipfs so we don't rely on bundlers to inject node stuff and prepare for webpack 5, we already worked with the maintainers from bl, readable-stream, leveldb, etc to make this a reality would be really important to have simple-peer too.

[EricEisaman]

I agree. As we prepare for Deno to take the stage, removing anything Node specific is a wise choice.

[feross]

@hugomrdias Can you link the PRs from those other projects so we can take a look?

[hugomrdias]

Level/level-js#191
Level/abstract-leveldown#362
rvagg/bl#81
nodejs/readable-stream#435 (this one is still wip but not because of buffer)

[nazar-pc]

Can't we have ./buffer.js that will re-export native Buffer in Node.js and polyfill in browsers using browser field in package.json?

[hugomrdias]

The changes in the PR basically do that, but the node/browser dance is inside the buffer package.

[vasco-santos]

Hey folks! Is there any update on this?

[t-mullen]

@feross I disagree with the revert of this PR.

require('buffer') always uses the Node.js buffer, ignoring the buffer package from npm which is installed in node_modules. To use the npm version, you need to do require('buffer/').

We never used the NPM module before in Node.js and this PR does not change that. The intent here is not to start using the NPM version either. There's no change in Node.js here.

We don't actually want to use the npm version when running in Node.js since it's less efficient and compatible than the built-in Buffer.

I agree, and this PR doesn't stop using native buffer or intend that.

The only change here is with the browser. Currently browserify will see require('buffer') and automatically inject the NPM version. Not all bundlers do this and will fail due to the non-existent buffer dependency. Adding the dependency explicitly will allow these bundlers to work.

[feross]

@t-mullen Yep, you're right. I just reverted my revert and shipped this in 9.9.0.