npm install fails due to missing gyp build dependencies

[TheSeven]

On Ubuntu 18.04 (and I assume most other Debian-based systems as well), node-gyp will require the make and g++ packages to build native nodejs packages required by cryptpad.

[TheSeven]

Upon further inspection it looks like these packages might be pulled in by a recommendation from node-gyp on some systems, so this may work on a default installation of Ubuntu. Can't hurt to depend on these ones directly though, to fix systems which ignore recommendations.

[t2d]

Thank you for pointing this out. A pull request would be very welcome.