Browser environment (webpack) support

[slavafomin]

Hello!

Right now, minimatch includes the following code:

var path = { sep: '/' }
try {
  path = require('path')
} catch (er) {
}

https://github.com/isaacs/minimatch/blob/master/minimatch.js#L4-L7

However, it doesn't work very well with the bundling tools like Webpack, because they need to resolve all the dependencies during the build time and not at runtime. Also, the browser environment doesn't has path module built-in.

This causes the following error in Webpack:

WARNING in …/node_modules/minimatch/minimatch.js 6:9-24
Module not found: Error: Can't resolve 'path' in '…/node_modules/minimatch'

BREAKING CHANGE: webpack < 5 used to include polyfills for node.js core modules by default.
This is no longer the case. Verify if you need this module and configure a polyfill for it.

If you want to include a polyfill, you need to:
	- add a fallback 'resolve.fallback: { "path": require.resolve("path-browserify") }'
	- install 'path-browserify'
If you don't want to include a polyfill, you can use an empty module like this:
	resolve.fallback: { "path": false }

Of course, we don't want to load polyfill just to satisfy the minimatch (which is using only the sep property from the path module) and we can't substitute it with the empty module also because it will break the minimatch logic.

I would suggest to introduce a more browser/bundler friendly approach.

[isaacs]

Since all we use is path.sep, yeah, it seems like a better approach could be found.

Maybe it could do require('./lib/path.js') and that module could be something like:

module.exports = typeof process === 'object' && process && process.platform === 'win32'
  ? { sep: '\\' } : { sep: '/' }

It is handy to have it as a separate module so that it can be easily mocked in tests.