Mention fcrepo.session.timeout property.

[rosiel]

Purpose / why

Saw this on Slack and thought it should be documented.

What changes were made?

• mention how to change fcrepo.session.timeout if you're loading large files
• add headers so that it makes sense and for accessibility.

Verification

Is this accurate?

Interested Parties

@whikloj @ruebot

Checklist

Pull-request Reviewer

Pull-request reviewer should ensure the following:

• Does this PR link to related issues?
• Does the proposed documentation align with the Islandora Documentation Style Guide?
• Are the changes accurate, useful, free of typos, etc?

Person Merging

The person merging should ensure the following:

• Does mkdocs still build successfully? (This is indicated by TravisCI passing. To test locally, and see warnings, see How To Build Documentation.)
• If pages are renamed or removed, have all internal links to those pages been fixed?
• If pages are added, have they been linked to or placed in the menu?
• Did the PR receive at least one approval from a committer, and all issues raised have been addressed?

[ruebot]

mjordan/islandora_workbench#353

[whikloj]

One little typo but otherwise makes sense.

[ruebot]

@rosiel I added a couple more configuration points in mjordan/islandora_workbench#353 if you want to update this PR with them.

[whikloj]

One more typo (I think), otherwise its good

[whikloj]

👍