🍱 MQT Branding on RtD (#603)

## Description

This PR slighly adjusts the RtD configuration so that less files have to
be copied over to all repositories.

## Checklist:

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- [x] The pull request only contains commits that are related to it.
- [x] I have added appropriate tests and documentation.
- [x] I have made sure that all CI jobs on GitHub pass.
- [x] The pull request introduces no new warnings and follows the
project's style guidelines.

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Signed-off-by: burgholzer <[email protected]>

README.md

@@ -81,16 +81,16 @@ Munich Quantum Valley, which is supported by the Bavarian state government with
 <p align="center">
 <picture>
 <source media="(prefers-color-scheme: dark)" srcset="https://raw.githubusercontent.com/cda-tum/mqt/main/docs/_static/tum_dark.svg" width="28%">
-<img src="https://raw.githubusercontent.com/cda-tum/mqt/main/docs/_static/tum_light.svg" width="28%">
+<img src="https://raw.githubusercontent.com/cda-tum/mqt/main/docs/_static/tum_light.svg" width="28%" alt="TUM Logo">
 </picture>
 <picture>
-<img src="https://raw.githubusercontent.com/cda-tum/mqt/main/docs/_static/logo-bavaria.svg" width="16%">
+<img src="https://raw.githubusercontent.com/cda-tum/mqt/main/docs/_static/logo-bavaria.svg" width="16%" alt="Coat of Arms of Bavaria">
 </picture>
 <picture>
 <source media="(prefers-color-scheme: dark)" srcset="https://raw.githubusercontent.com/cda-tum/mqt/main/docs/_static/erc_dark.svg" width="24%">
-<img src="https://raw.githubusercontent.com/cda-tum/mqt/main/docs/_static/erc_light.svg" width="24%">
+<img src="https://raw.githubusercontent.com/cda-tum/mqt/main/docs/_static/erc_light.svg" width="24%" alt="ERC Logo">
 </picture>
 <picture>
-<img src="https://raw.githubusercontent.com/cda-tum/mqt/main/docs/_static/logo-mqv.svg" width="28%">
+<img src="https://raw.githubusercontent.com/cda-tum/mqt/main/docs/_static/logo-mqv.svg" width="28%" alt="MQV Logo">
 </picture>
 </p>