add identified loose html files into existing "content/" structure

[njr2128]

As per issue #17, loose html files were assessed and a number were identified and should now be added/moved to their correct location in the new content/ S3 structure.

The loose html files have been catalogued in the GD sheet, 2021-07-14_S3-content/index. In the column "Action," files that have been identified have values that start with "Add to" + "[semester+year]". Greg should now go through these and move them to their correct directory based on the information in the "Action" column and any additional info needed from the "Notes" column.

[gschare]

Also make sure to add these new renamings to the table (final_mapping.csv)

[gschare]

The ones with "Add to" in their action column have been completed.