Add GitHub Pages workflow & rename to `index.html`

[paddyroddy]

Description

This will mean that the slides appear at https://scikit-surgery.github.io/cmicHACKS2 rather than https://scikit-surgery.github.io/cmicHACKS2/slides/slides.html. And means any new change will be deployed.

Type of change

Please delete options accordingly to the description.

• [ ] Bug fix (non-breaking change which fixes an issue)
• [X] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] This change requires a documentation update

Checklist

• [X] I have read the CONTRIBUTING docs and have a developer setup (especially important are pre-commitand pytest)
• [X] My code is properly tested
• [X] My code follows the style guidelines
• [X] My code does not contain unused elements. If so, I documented why it needs to.
• [X] My changes generate no new warnings
• [X] I have performed a self-review of my own code
• [X] I have commented my code, particularly in hard-to-understand areas
• [X] I have made corresponding changes to the documentation
• [X] This pull request is ready to be reviewed
• [X] My branch is up-to-date with master (with use of rebase if needed)
• [X] If the PR is ready and there are multiple commits, I have squashed them and force-pushed

[paddyroddy]

Thanks Paddy, it looks great! Just realised that scikit-surgery.github.io/cmicHACKS2 is not showing demo video

Let me have a look