Set uri gem minimum version to 0.12.0

Otherwise unit tests will fail with Ruby 3.0,
because it bundled an older version that didn't support
URI.decode_uri_component method.

https://bugs.ruby-lang.org/issues/9045
ruby/uri@16cfc4e92f

Gemfile.lock

@@ -5,6 +5,7 @@ PATH
       ed25519 (~> 1.3, >= 1.3.0)
       rack (~> 3.0)
       starry (~> 0.1)
+      uri (>= 0.12.0)
 
 GEM
   remote: https://rubygems.org/
@@ -69,6 +70,7 @@ GEM
       rubocop-performance (~> 1.20.2)
     starry (0.1.0)
     unicode-display_width (2.5.0)
+    uri (0.13.0)
 
 PLATFORMS
   arm64-darwin-21

lib/linzer.rb

@@ -3,6 +3,7 @@
 require "starry"
 require "openssl"
 require "rack"
+require "uri"
 
 require_relative "linzer/version"
 require_relative "linzer/common"

linzer.gemspec

@@ -32,4 +32,5 @@ Gem::Specification.new do |spec|
   spec.add_runtime_dependency "ed25519", "~> 1.3", ">= 1.3.0"
   spec.add_runtime_dependency "starry", "~> 0.1"
   spec.add_runtime_dependency "rack", "~> 3.0"
+  spec.add_runtime_dependency "uri", ">= 0.12.0"
 end