Issue 217: Resolve check notes

[athowes]

Description

This PR closes #217.

Checklist

• My PR is based on a package issue and I have explicitly linked it.
• I have included the target issue or issues in the PR title in the for Issue(s) issue-numbers: PR title
• I have read the contribution guidelines.
• I have tested my changes locally.
• I have added or updated unit tests where necessary.
• I have updated the documentation if required.
• My code follows the established coding standards.
• I have added a news item linked to this PR.
• I have reviewed CI checks for this PR and addressed them as far as I am able.

[athowes]

NOTES left not fixable so that's it I think:

❯ checking for portable file names ... NOTE
  Found the following non-portable file paths:
    epidist/vignettes/approx-inference_cache/html/load-requirements_84057c410b1cb58565e050358d587b14.RData
    epidist/vignettes/approx-inference_cache/html/unnamed-chunk-10_c05e04f0bcd6b4afba009ba5d2b07acf.RData
  
  Tarballs are only required to store paths of up to 100 bytes and cannot
  store those of more than 256 bytes, with restrictions including to 100
  bytes for the final component.
  See section ‘Package structure’ in the ‘Writing R Extensions’ manual.

❯ checking installed package size ... NOTE
    installed size is  7.0Mb
    sub-directories of 1Mb or more:
      doc              3.3Mb
      gadm41_SLE_shp   3.3Mb

❯ checking dependencies in R code ... NOTE
  Unexported objects imported by ':::' calls:
    ‘brms:::dpar_bounds’ ‘brms:::validate_data’ ‘brms:::validate_family’
    ‘brms:::validate_formula’
    See the note in ?`:::` about the use of this operator.

[seabbs]

LGTM