Add solution to the 2021 midterm

previous-exams/2021-midterm/m2/assignment.sbt

previous-exams/2021-midterm/m2/build.sbt

previous-exams/2021-midterm/m2/grading-tests.jar

...ams/2021-midterm/m2/project/FilteringReporterPlugin.scala

previous-exams/2021-midterm/m2/project/MOOCSettings.scala

previous-exams/2021-midterm/m2/project/StudentTasks.scala

previous-exams/2021-midterm/m2/project/build.properties

previous-exams/2021-midterm/m2/project/buildSettings.sbt

previous-exams/2021-midterm/m2/project/plugins.sbt

previous-exams/2021-midterm/m2/src/main/scala/m2/Lib.scala

previous-exams/2021-midterm/m2/src/main/scala/m2/M2.scala

...ous-exams/2021-midterm/m2/src/test/scala/m2/M2Suite.scala

previous-exams/2021-midterm/m20.md

previous-exams/2021-midterm/m20/.gitignore

previous-exams/2021-midterm/m20/assignment.sbt

previous-exams/2021-midterm/m20/build.sbt

previous-exams/2021-midterm/m20/grading-tests.jar

...ms/2021-midterm/m20/project/FilteringReporterPlugin.scala

previous-exams/2021-midterm/m20/project/MOOCSettings.scala

previous-exams/2021-midterm/m20/project/StudentTasks.scala