Add information on MARC syntax used in various tools

[abigailsparling]

How could the content be improved?

Make clear the difference in MARC syntax (where to use =, where to record field number, spaces, indicators, subfields, etc.) between find and replace, edit tools, and find and replace.

Add intro to syntax and importance for tools in lesson 3, cover specific syntax for tools in lesson 5/6

[abigailsparling]

Update 05-profiling-your-MARC-data.md to add note about use of = in the find function

[abigailsparling]

@abigailsparling take lesson 3 and 5

[abigailsparling]

lessons 3 & 5 updated

[abigailsparling]

Closed with recent PRs