Update lab material

[bohyunjung]

@sourabhbagrecha This PR includes some crucial changes for the lab.

2aa9bf6

• implements https://github.com/mongodb-developer/docusaurus-workshop/pull/11 to fix malformed footer items.

9e4e76f

This commit includes the suggestion by sis0k0: #16

• fixes some lab codes that won't run against the DB included in jedee
• For example, db.books.find({ genres: "Science" }) doesn't work as the document structure in jedee is as follows.

"genre": [
  {
    "genreId": 5639,
    "name": "Police"
  }
]

3c4e1d9

• changes the challenge question for the significant sort result
  • max numAuthors is now 8, as it was 2
• Check if the authors field exists before getting the size
  • Otherwise, the lab environment yields the error as below due to the documents without the authors field.

PlanExecutor error during aggregation :: caused by :: The argument to $size must be an array, but was of type: missing