Update documentation and permalinks for consistency and clarity

- Changed references in markup.md to update "data.html" to "data/" for clarity.
- Updated metadata.md to correct the link to the general documentation.
- Modified navbar.md to ensure stub values match the new permalink structure.
- Adjusted tables.md to reflect the new permalink for the table visualization page.
- Updated about.md to change the permalink from "/about.html" to "/about/" and revised content for clarity and impact.
- Changed browse.md permalink from "/browse.html" to "/browse/" for consistency.
- Added copyright.md page with copyright information and terms of use.
- Updated data.md to change permalink from "/data.html" to "/data/" and added introductory content.
- Created donate.md page to facilitate donations and acknowledge supporters.
- Updated locations.md permalink from "/locations.html" to "/locations/" for consistency.
- Changed map.md permalink from "/map.html" to "/map/" for uniformity.
- Added erasure.md page discussing the historical context of Black queer Kansas Citians.
- Updated out-there.md to correct the link to Lea Hopkins' interview.
- Changed subjects.md permalink from "/subjects.html" to "/subjects/" for consistency.
- Updated timeline.md permalink from "/timeline.html" to "/timeline/" for uniformity.

_includes/item/browse-buttons.html

@@ -7,7 +7,7 @@
 {%- endcomment -%}
 <div class="text-center">
   <a class="btn btn-secondary" href="{{ page.previous_item | relative_url }}" id="prev-page-button">&laquo; Previous</a>
-  <a class="btn btn-secondary" href="{{ '/browse.html' | relative_url }}">Back to Browse</a>
+  <a class="btn btn-secondary" href="{{ '/browse/' | relative_url }}">Back to Browse</a>
   <a class="btn btn-secondary" href="{{ page.next_item | relative_url }}" id="next-page-button">Next &raquo;</a>
 </div>
 <div id="item-nav">