Add p-cancelable module

https://github.com/sindresorhus/p-cancelable

readme.md

@@ -38,6 +38,7 @@ I intend to use this space to document my promise modules, useful promise patter
 - **[p-pipe](https://github.com/sindresorhus/p-pipe)**: Compose promise-returning & async functions into a reusable pipeline
 - **[p-props](https://github.com/sindresorhus/p-props)**: Like `Promise.all()` but for `Map` and `Object`
 - **[p-waterfall](https://github.com/sindresorhus/p-waterfall)**: Run promise-returning & async functions in series, each passing its result to the next
+- **[p-cancelable](https://github.com/sindresorhus/p-cancelable)**: Create a promise that can be canceled
 - **[p-reflect](https://github.com/sindresorhus/p-reflect)**: Make a promise always fulfill with its actual fulfillment value or rejection reason
 - **[p-filter](https://github.com/sindresorhus/p-filter)**: Filter promises concurrently
 - **[p-reduce](https://github.com/sindresorhus/p-reduce)**: Reduce a list of values using promises into a promise for a value