Rename CLI options and change default Pagefind URL

[bglw]

This PR contains the main breaking(ish) changes for Pagefind 1.0

• The default location that Pagefind outputs files to is now /pagefind/ instead of /_pagefind/
  • Reasoning: Some hosting providers do not host directories that lead with an underscore by default:

  • 188

  • Backwards compat: This is the main breaking change being introduced for 1.0.
  • In this PR, Pagefind will look at pages as it is indexing and see if it encounters any CSS or JS links with a /_pagefind/... URL. If one is found, then Pagefind will output all search files to both /pagefind/ and /_pagefind/.
  • This approach will miss any setups where the page with search assets is excluded by a glob, or sites where the JS API is used directly from a script.
  • My hope is that the majority of sites are using the default UI, and sites using a more advanced setup are more likely to be setting a custom directory, or be pinning the version of Pagefind they run such that a conscious 1.0 migration is possible.
• The --bundle-dir option has been renamed to --output-subdir
  • Reasoning: This option was repeatedly confusing:
  • #68
  • #138
  • Backwards compat: --bundle-dir is still honoured (and warned on)
• A --output-path option that is not relative to the indexed site has been introduced
  • Reasoning: Not a breaking change, but a new addition to help clarify the above option
• The --source option has been renamed to --site for clarity
  • Reasoning: By default Pagefind modifies this directory, which is unusual for a source directory. site is more neutral.
  • Mentioned in #68
  • Backwards compat: --source is still honoured (and warned on)
  • Backwards compat: -s now aliases to site instead of source