Update documentation to recommend pak::pak instead of devtools::install_github

[Andrew0Hill]

It looks like devtools::install_github is deprecated, but this is currently the recommended way to install CIDAtools.

Andrew to:

1. Verify that suggested replacement pak::pak works as expected.
2. Update documentation to reflect the change.

[abhinavvpundirr]

Replaced devtools::install_github('CIDA-CSPH/CIDAtools') with pak::pak('CIDA-CSPH/CIDAtools') in both README.md and README.qmd. Updated the commented install line from install.packages("devtools") to install.packages("pak").
Also updated the create_project() usage example in both READMEs to reflect the now-required project_name and analyst arguments (from #52).