Move py.typed up into stactools dir

[jsignell]

Related Issue(s): Closes #444

Description: My understanding is that these files need to live at the top

PR checklist:

• [x] Code is formatted (run scripts/format).
• [x] Code lints properly (run scripts/lint).
• [x] Tests pass (run scripts/test).
• [x] Documentation has been updated to reflect changes, if applicable.
• [x] Changes are added to the CHANGELOG.

[gadomski]

I think #452 is the way to do it.