Update @types/node to 15.0.1

[Steven Black]

Expected Behavior

Not especially applicable. $ yarn outdated presently returns one package, @types/node which has recently been upgraded to 15.0.1.

Since this is a boilerplate, it's easy to keep things current.

Steps to Reproduce the Problem

$ yarn outdated
yarn outdated v1.22.10
info Color legend :
 "<red>"    : Major Update backward-incompatible updates
 "<yellow>" : Minor Update backward-compatible features
 "<green>"  : Patch Update backward-compatible bug fixes
Package     Current  Wanted   Latest Package Type    URL
@types/node 14.14.43 14.14.43 15.0.1 devDependencies https://github.com/DefinitelyTyped/DefinitelyTyped.git
✨  Done in 1.98s.