feat: add KUBO_BINARY env to allow overriding the path used (#62)

Refs: ipfs/kubo#10013

---------

Co-authored-by: Alex Potsides <alex@achingbrain.net>

README.md

@@ -50,6 +50,12 @@ An error will be thrown if the path to the binary cannot be resolved.
 
 Downloaded archives are placed in OS-specific cache directory which can be customized by setting `NPM_GO_IPFS_CACHE` in env.
 
+### Overriding with `KUBO_BINARY` env
+
+If the `KUBO_BINARY` env variable is set at runtime this will override the path of the binary used.
+
+This must point to the file, not the directory containing the file.
+
 ## Development
 
 **Warning**: the file `bin/ipfs` is a placeholder, when downloading stuff, it gets replaced. so if you run `node install.js` it will then be dirty in the git repo. **Do not commit this file**, as then you would be commiting a big binary and publishing it to npm. A pre-commit hook exists and should protect against this, but better safe than sorry.

src/index.js

@@ -4,6 +4,10 @@ const fs = require('fs')
 const path = require('path')
 
 module.exports.path = function () {
+  if (process.env.KUBO_BINARY) {
+    return process.env.KUBO_BINARY
+  }
+
   const paths = [
     path.resolve(path.join(__dirname, '..', 'go-ipfs', 'ipfs')),
     path.resolve(path.join(__dirname, '..', 'go-ipfs', 'ipfs.exe'))