Deploy develop branch documentation to /develop subpath

[ReeceHumphreys]

• Tickets addressed: N/A
• Review: By commit
• Merge strategy: Merge (no squash)

Description

Updates the merge workflow to deploy the documentation to the /develop subpath when when merging PRs into the develop branch and to deploy docs to / when merging to the master branch. This will have the behavior of having the current docs site being updated less frequently and will only reflect the current state of the master branch.

Verification

I created a repo mimicking the setup of the deploy action we use for Basilisk for testing at https://github.com/ReeceHumphreys/deploy-test:

• You can see that https://reecehumphreys.github.io/deploy-test/develop/ contains the latest source file from the index.rst in the develop branch.
• This is opposed to https://reecehumphreys.github.io/deploy-test/ which contains the latest source file from the index.rst in the main branch.

Caution

I will delete the repo mentioned in the Verification section when this PR is merged so the link may break.

Documentation

N/A

Future work

We could theoretically maintain documentation for each major release using this strategy. So we could have /3.8, 3.9, etc.
This would require keeping extra branches around though which we probably don't want to do.

[schaubh]

Some quick questions and comments.

[schaubh]

Good to go.