added install swanky node command

[shunsukew]

For those who initialize projects without local swanky node but later would like to use.

[kziemianek]

Looks like great feature.

In our case we ended up pushing swanky-node to git repository (not included in .gitignore). With recent release of swanky-node 1.4.0 which size is greater than 100 mb we cannot push it to GitHub anymore due to limits.

Generally I was sceptic about pushing binary to GitHub, but with this feature we will probably remove it because we will be able to download node with this command after cloning repository.

Additionally to this feature I would love to see some kind of swanky-node version locking mechanism (like package.lock.json) to share the same node across devs ends.

[shunsukew]

Thank you so much for the feedback!

Additionally to this feature I would love to see some kind of swanky-node version locking mechanism (like package.lock.json) to share the same node across devs ends.

That would be a great feature, I assume that can be part of swanky.config.json. If version is already defined, install that version of node instead of the latest one.
It's also feasible to specify a version with the command arg. swanky node install asks users if they would like to overwrite node binary, they can chose whichever version they want anytime.

eval prio
arg -> config file -> latest version by default

[codespool]

LGTM