Added rake tasks for Docker [skip ci]

Rakefile

@@ -8,3 +8,19 @@ Rake::TestTask.new(:test) do |t|
 end
 
 task default: :test
+
+namespace :docker do
+  task :build do
+    require_relative "lib/pgslice/version"
+
+    system "docker build --pull --no-cache --platform linux/amd64 -t ankane/pgslice:latest .", exception: true
+    system "docker build --platform linux/amd64 -t ankane/pgslice:v#{PgSlice::VERSION} .", exception: true
+  end
+
+  task :release do
+    require_relative "lib/pgslice/version"
+
+    system "docker push ankane/pgslice:latest", exception: true
+    system "docker push ankane/pgslice:v#{PgSlice::VERSION}", exception: true
+  end
+end