Adding rst for TetrahedraUP element and Triangular UP elements - #208

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@v3, actions/upload-artifact@v4. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

Inline interpreted text or phrase reference start-string without end-string.

Inline interpreted text or phrase reference start-string without end-string.

Explicit markup ends without a blank line; unexpected unindent.

Title underline too short.

Title underline too short.

Footnote [1] is not referenced.

Title underline too short.

Inline interpreted text or phrase reference start-string without end-string.

Title underline too short.

Title overline too short.