text: Title: Edge case: `source file.xonshrc` shows `attempting to source non-xonsh file`
  Body: ```xsh
  echo 'echo ok' > file.xonshrc
  # RuntimeError: attempting to source non-xonsh file! If you are trying to source 
  # a file in another language, then please use the appropriate source command. 
  # For example, source-bash script.sh
  
  mv file.xonshrc file.xsh
  # ok
  ```
  
  We need to have an ability to source any xonsh file regardless extension.
  
  
  ## For community
  ⬇️  **Please click the 👍 reaction instead of leaving a `+1` or 👍  comment**
  