title: Delete full workspace or one variable in julia
body: <p>I have searched for a while and experimenting with CommonRLInterface <a href="https://github.com/JuliaReinforcementLearning/CommonRLInterface.jl" rel="noreferrer">https://github.com/JuliaReinforcementLearning/CommonRLInterface.jl</a>. There are some mutable variables. I am not an expert in Julia Programming, but I want to clear the whole workspace or delete a mutable variable (which is not allowed for mutable variables as far as I understand it, but in CommonRLInterface it comes from AbstractEnv superclass so I cannot change it).</p>
  <pre><code>struct myEnv &lt;: AbstractEnv 
  
  julia&gt; myGridWorld=Nothing
  ERROR: invalid redefinition of constant myGridWorld
  Stacktrace:
   [1] top-level scope
     @ none:1
  </code></pre>
  <p>I want to clear the whole workspace. So I have to stop julia and restart it again. In addition I have to activate the environment again.</p>
  <p>It would help me if there would exist a button or keyshortcut, which automatically resets the workspace, starting a new julia kernel if necessary and activates the last environment (maybe also restarting the code).</p>
  <p>There exists similar posts which were not helpful
  <a href="https://discourse.julialang.org/t/how-to-clear-variables-and-or-whole-work-space/10149" rel="noreferrer">https://discourse.julialang.org/t/how-to-clear-variables-and-or-whole-work-space/10149</a></p>