installing rustc/cargo for mybinder demo

[aleivag]

Summary

when we switch to the rust compiler by default, mybinder stop working, as reported in #1054 this is because the binder docker image does not have a rust compiler or tools, this install them by using the apt.txt file

Test Plan

if you go to https://mybinder.org/v2/gh/aleivag/LibCST/fix-binder?filepath=docs/source/tutorial.ipynb you'll see this works

[aleivag]

notice that this just fix the binder docker image creation... I think this is still missing installing python dependencies like typing_inspect , i plan to fix that part in a subsequent PR

EDIT: actually fixed in this PR

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (52bbff6) 91.09% compared to head (2060dfb) 91.09%.
Report is 3 commits behind head on main.

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Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1083   +/-   ##
=======================================
  Coverage   91.09%   91.09%           
=======================================
  Files         255      255           
  Lines       26564    26564           
=======================================
  Hits        24198    24198           
  Misses       2366     2366           

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[zsol]

<3