Cross-platform remove dist folder using rimraf in build script

[girish-io]

I was trying to build the package on a Windows system using npm run build. This however gave me the following error:

'rm' is not recognized as an internal or external command,
operable program or batch file.

This happened because the build script currently uses the unix command rm to remove the dist folder which doesn't exist on Windows.

I have replaced it with rimraf which allows us to remove the directory regardless of the platform we're developing on. This however introduces a new library and I'm not sure whether this is acceptable or not, so please let me know 😃

[davidcalhoun]

Great, thank you for this! Looks good.