add ruby example, update README.md

crates/servicepoint_binding_uniffi/libraries/ruby/servicepoint.gemspec

@@ -0,0 +1,13 @@
+Gem::Specification.new do |s|
+  s.name        = "servicepoint"
+  s.version     = "0.0.0"
+  s.summary     = ""
+  s.description = ""
+  s.authors     = ["kaesaecracker"]
+  s.email       = ""
+  s.files       = ["lib/servicepoint_binding_uniffi.rb"]
+  s.homepage    =
+    "https://rubygems.org/gems/hola"
+  s.license       = "MIT"
+  s.add_dependency 'ffi'
+end