add project and lab dirs

sum23/labs/README.md

+# Labs for CS 220 (summer 2023)
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+Labs will be added to this page throughout the semester, however, please do not start working on a particular lab before the day that it is scheduled for in lab. (The materials may be updated to better reflect what was discussed in lecture.)

sum23/projects/README.md

+# Projects for CS 220 (Summer 2023)
+
+Projects will be posted here by *9am on Tuesdays* (for projects due Fridays) and *9am on Thursdays* (for projects due Tuesdays). Please wait to begin projects until after that time (even if the project is already uploaded), as we may still be making changes to it. 
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