feature: Add ability for bot to send a cheatsheet for each submission

[Leonelmarianog]

Summary

• Added ability for robotina to send a cheatsheet document for each submission. If the lesson doesn't have a cheatsheet associated to it, it is not send.

[github-actions]

LCOV of commit 8af65ff during CI workflow #64

Summary coverage rate:
  lines......: 95.8% (565 of 590 lines)
  functions..: 98.6% (72 of 73 functions)
  branches...: 86.3% (157 of 182 branches)

Files changed coverage rate:
                                                                           |Lines       |Functions  |Branches    
  Filename                                                                 |Rate     Num|Rate    Num|Rate     Num
  ===============================================================================================================
  src/commands/tarea/tarea.ts                                              | 100%     61| 100%     3|95.0%     20
  src/events/reaction/handleRobotFaceReaction.ts                           |98.8%     82| 100%     2|96.4%     28
  src/utils/assignmentCheatsheet.ts                                        | 100%      1|    -     0|    -      0