Add a cut off for size of text to add to ES

[karindalziel]

we have found that more than a million characters in the text field makes ES choke. Probably the best way to go about this would be to have a max size in the config, and then call that in the script (just in case we discover performance issues at different ingest sizes.)

Also add a note to the log/output that the file was truncated so we can split it up, which should be best practice anyway.

[techgique]

This issue links to a couple related PRs for code to reference: https://github.com/whitmanarchive/whitman-issues/issues/665