doc: add REUSE license information (#1361)

* doc: add REUSE comment headers

* doc: add REUSE comment headers for mkDocs overrides

The original license text was moved to the LICENSES directory
and the MIT license identifier was used since only encoding differences
to the MIT license were present.

Further, the existing copyright notice was moved to SPDX-FileCopyrightText
and one for the TagStudio Contributors was added since the files are not
entirely the same as the originals in the mkdocs-material project.

* doc: add license information files for the translations

* doc: add licence file for oxanium font

As stated on [Google Fonts](https://fonts.google.com/specimen/Oxanium/license), this font is licensed under OFL-1.1.

* doc: re-license flow_layout.py to GPL-3.0-only

This is possible because the Qt example this is based on can be licensed
under BSD-3-Clause which is GPL-3.0 compatible.

* doc: add REUSE comment header for singleton.py

Comparing our implementation with the one it is based on, they really
don't have much more in common than the general idea of the
implementation, which afaik can't be copyrighted.

* doc: Add REUSE comment header for blender_renderer.py

We can plainly license this under GPL-3.0 according to https://www.blender.org/about/license/

* doc: add REUSE comment headers to vendored files

* doc: add REUSE comment header for rounded_pixmap_style.py

Source of name for copyright notice:
Answer by eyllanesc: https://stackoverflow.com/users/6622587/eyllanesc
Profile links to Github: https://github.com/eyllanesc

Stackoverflow licensing: https://stackoverflow.com/help/licensing

* doc: add REUSE comment headers

* doc: add license information file for icon_mono.svg

* doc: add REUSE comment header for files in .github

* doc: add REUSE.toml to give license information for various files without spamming .license files

* fix: use type parameter instead of subclass

* doc: add entries for remaining files in REUSE.toml

According to info from github comment by CyanVoxel: https://github.com/TagStudioDev/TagStudio/pull/1361#issuecomment-4423632570

* ci: add REUSE check workflow

Src: 'https://reuse.software/dev/#github-actions'

* doc: add missing license

* doc: fix license for material-design-icons

* license: change license to MIT for two files only changes by Computerdores and CyanVoxel

* doc: remove unnecessary .license files

* doc: fix incorrect license entries

* doc: add missing license doc

nix/package/default.nix

@@ -1,3 +1,7 @@
+# SPDX-FileCopyrightText: (c) TagStudio Contributors
+# SPDX-License-Identifier: GPL-3.0-only
+
+
 {
   ffmpeg-headless,
   lib,

nix/package/pillow-jxl-plugin.nix

@@ -1,3 +1,7 @@
+# SPDX-FileCopyrightText: (c) TagStudio Contributors
+# SPDX-License-Identifier: GPL-3.0-only
+
+
 {
   buildPythonPackage,
   cmake,

nix/package/pyexiv2.nix

@@ -1,3 +1,7 @@
+# SPDX-FileCopyrightText: (c) TagStudio Contributors
+# SPDX-License-Identifier: GPL-3.0-only
+
+
 {
   autoPatchelfHook,
   buildPythonPackage,

nix/shell.nix

@@ -1,3 +1,7 @@
+# SPDX-FileCopyrightText: (c) TagStudio Contributors
+# SPDX-License-Identifier: GPL-3.0-only
+
+
 {
   lib,
   pkgs,