Add placeholder for future Solr Rake tasks
user
```ruby
#!/usr/bin/env ruby
# The ASF licenses this file to You under the Apache License, Version 2.0
# (the "License"); you may not use this file except in compliance with
# the License.  You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

# TODO: fill out Solr tasks: start, stop, ping, optimize, etc.

require 'rake'
require 'rake/tasklib'

module Solr
  namespace :solr do
    desc "Start Solr"
    task :start do
      # TODO: actually start it up!
      puts "Starting..."
    end
  end
end
```
assistant