Add local 3D model viewer (three.js + occt-import-js) for STEP/STL, 8px box + caption; embed guide; licenses

THIRD_PARTY_LICENSES.md

@@ -9,6 +9,8 @@ The following files in this repository are **not** covered by the GPL-3.0 and ke
 | `lib/hljs_line_numbers.js` | [highlightjs-line-numbers](https://github.com/yury-dymov/highlightjs-line-numbers) | [MIT](#mit-license) |
 | `theme/cookie.woff2` | "Cookie" font, © 2011 [Ania Kruk](https://fonts.google.com/specimen/Cookie) | [SIL Open Font License 1.1](https://openfontlicense.org/) |
 | `assets/palette.png` | Gruvbox palette image from [morhetz/gruvbox](https://github.com/morhetz/gruvbox) (repo: MIT) | [MIT](#mit-license) |
+| `lib/3d/three.min.js`, `lib/3d/OrbitControls.js`, `lib/3d/STLLoader.js` | [three.js](https://github.com/mrdoob/three.js) r128 | [MIT](#mit-license) |
+| `lib/3d/occt-import-js.js`, `lib/3d/occt-import-js.wasm` | [occt-import-js](https://github.com/kovacsv/occt-import-js) (OpenCASCADE, WASM) | [LGPL-2.1](#lgpl-21) |
 | `scripts/bmc_button.js` | embeds the Trilium logo (SVG) from [Trilium/TriliumNext](https://github.com/TriliumNext/Trilium) | [AGPL-3.0](https://www.gnu.org/licenses/agpl-3.0.txt) |
 
 ## BSD-3-Clause
@@ -76,6 +78,12 @@ The full license text is available at <https://openfontlicense.org/> or
 
 Copyright (c) 2011 by Ania Kruk, with Reserved Font Name "Cookie".
 
+## LGPL-2.1
+
+`occt-import-js` is distributed under the GNU Lesser General Public License v2.1
+(<https://www.gnu.org/licenses/old-licenses/lgpl-2.1.html>). OpenCASCADE is LGPL-2.1 as well;
+the WASM blob is loaded at runtime by `scripts/3d_model_viewer.js` and is not statically linked.
+
 ## AGPL-3.0
 
 The Trilium logo embedded in `scripts/bmc_button.js` belongs to the Trilium /