Change edit link path to main.

[rosiel]

Purpose / why

Fix #1546 - the links to edit the documentation were set to 'master' not main.

The mkdocs documentation shows it needs to be set in the mkdocs config, or it defaults to master.

What changes were made?

set 'edit_uri' which mkdocs defaulted to edit/master/docs/ to be edit/main/docs.

Verification

Do the links work?

Interested Parties

@Islandora/8-x-committers

---

Checklist

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 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?

[rosiel]

ping @Islandora/8-x-committers

If someone could mkdocs build and mkdocs serve and see that the links go to the main branch, like they do when I serve it locally, that's be great.

If you haven't used mkdocs before, it's pretty simple! Ping me on slack and I'll help you set it up.

[jordandukart]

Link is nice and updated. Doing a quick grep there's quite a few other instances referring to the master branch directly in the docs. Should this be handled in this issue or a separate one?

[dannylamb]

I've got an open PR for that @jordandukart, feel free to merge this one.

[jordandukart]

@dannylamb mentioned in Slack another pull coming for those issues so merging this.