harper-ls ci workflow

[s-sajid-ali]

Set up a new CI workflow with Harper: https://writewithharper.com/docs/about

Fix common grammatical errors and enforce a uniform style. For instance per @RobJY, there are a few places where we don't follow the same capitalization rule for section headings:

• Renewing your HPC Account -> Renewing Your HPC Account
• How to request an HPC account -> How to Request an HPC Account

[s-sajid-ali]

Also investigate vale as an alternative: https://github.com/vale-cli/vale