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/data-download-modal.html

@@ -1,7 +1,7 @@
 {% comment %}
     This include creates a modal pop up with data export options.
     The logic of which formats appear is based on config-nav stubs:
-    if subject.html, map.html, location.html, or timeline.html are present, 
+    if subject.html, map/, location.html, or timeline.html are present, 
     corresponding data formats will be available for download.
 {%- endcomment -%}