Add more license headers

.gitignore

+# SPDX-FileCopyrightText: 2024 Phil Höfer <phil@suma-ev.de>
+# SPDX-License-Identifier: AGPL-3.0-only
+
 # Rust build directory
 /target/
 

doc/README.md

+<!--
+SPDX-FileCopyrightText: 2024 Phil Höfer <phil@suma-ev.de>
+
+SPDX-License-Identifier: AGPL-3.0-only
+-->
 # Introduction
 
 Suggestible is software toolbox for creating an auto-suggestion endpoint from a search query log file.

doc/SUMMARY.md

+<!--
+SPDX-FileCopyrightText: 2024 Phil Höfer <phil@suma-ev.de>
+
+SPDX-License-Identifier: AGPL-3.0-only
+-->
 # Summary
 
 [Introduction](README.md)

doc/user/howto_basic.md

+<!--
+SPDX-FileCopyrightText: 2024 Phil Höfer <phil@suma-ev.de>
+
+SPDX-License-Identifier: AGPL-3.0-only
+-->
 # Using Suggestible ◇
 This how-to helps you set up Suggestible using your own data.
 

doc/user/howto_build.md

+<!--
+SPDX-FileCopyrightText: 2024 Phil Höfer <phil@suma-ev.de>
+
+SPDX-License-Identifier: AGPL-3.0-only
+-->
 # Building Suggestible ◇

doc/user/index.md

+<!--
+SPDX-FileCopyrightText: 2024 Phil Höfer <phil@suma-ev.de>
+
+SPDX-License-Identifier: AGPL-3.0-only
+-->
 # Overview
 
 ## Reading Journeys

doc/user/ref_config.md

+<!--
+SPDX-FileCopyrightText: 2024 Phil Höfer <phil@suma-ev.de>
+
+SPDX-License-Identifier: AGPL-3.0-only
+-->
 # Configuration Options ❖

doc/user/ref_predmodels.md

+<!--
+SPDX-FileCopyrightText: 2024 Phil Höfer <phil@suma-ev.de>
+
+SPDX-License-Identifier: AGPL-3.0-only
+-->
 # Prediction Models ❖

doc/user/tutorial_basic.md

+<!--
+SPDX-FileCopyrightText: 2024 Phil Höfer <phil@suma-ev.de>
+
+SPDX-License-Identifier: AGPL-3.0-only
+-->
 # Trying out Suggestible