feat: use import { Buffer } from 'buffer/' to be compatible with Bun

[lht102]

currently, the node-casbin is not compatible with Bun when running bun build

$ bun build src/index.ts --outdir ./build
28 | import { Buffer } from 'buffer';
              ^
error: No matching export in "node:buffer" for import "Buffer"
    at /.../node_modules/casbin/lib/esm/util/ip.js:28:10
error: script "build" exited with code 1

there is a open issue about buffer import with Bun: oven-sh/bun#8683

according to feross/buffer docs

To require this module explicitly, use require('buffer/') which tells the node.js module lookup algorithm (also used by browserify) to use the npm module named buffer instead of the node.js core module named buffer!

by adding trailing slash, this will use the feross/buffer module explicitly which works with Bun.

[casbin-bot]

@nodece @Shivansh-yadav13 please review

[CLAassistant]

All committers have signed the CLA.

[hsluoyz]

@lht102 fix CI:

[github-actions]

🎉 This PR is included in version 5.32.0 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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