Package updates for v0.4.0 release

[joshwlambert]

This PR closes #167 and closes #100 by making a range of minor updates to submit the package to CRAN and release v0.4.0. Updates include:

• adding cran-comments.md
• incrementing the minor version number
• removing {epiparameter} as a remote dependency
• adding installation instructions for CRAN and R-universe
• updating URLs that have changed
• updating tests/testthat/testdata/

[github-actions]

This pull request:

• Adds 1 new dependencies (direct and indirect)
• Adds 1 new system dependencies
• Removes 1 existing dependencies (direct and indirect)
• Removes 1 existing system dependencies

Reach out on slack (#code-review or #help channels) to double check if there are base R alternatives to the new dependencies.

(Note that results may be inaccurate if you branched from an outdated version of the target branch.)

[github-actions]

This pull request:

• Adds 1 new dependencies (direct and indirect)
• Adds 1 new system dependencies
• Removes 1 existing dependencies (direct and indirect)
• Removes 1 existing system dependencies

Reach out on slack (#code-review or #help channels) to double check if there are base R alternatives to the new dependencies.

(Note that results may be inaccurate if you branched from an outdated version of the target branch.)