Ship only minimal files in the gem

Prior to this the resulting gem included many unrelated files for real
use cases, such as CI files. This only includes the files relevant to
run it, plus some files you should ship.

Author: ekohl

fog-proxmox.gemspec

@@ -32,7 +32,7 @@ Gem::Specification.new do |spec|
   spec.homepage      = 'https://github.com/fog/fog-proxmox'
   spec.license       = 'GPL-3.0'
 
-  spec.files         = `git ls-files -z`.split("\x0")
+  spec.files         = `git ls-files -z CHANGELOG.md LICENSE README.md docs examples lib spec`.split("\x0")
   spec.executables   = spec.files.grep(%r{^bin/}) { |f| File.basename(f) }
   spec.require_paths = ['lib']
   spec.required_ruby_version = '>= 2.5'