Docs: Update Discord invite link

- The link is now permanent

Signed-off-by: Andrej Orsula <[email protected]>

README.md

@@ -4,14 +4,11 @@
   <a href="https://AndrejOrsula.github.io/space_robotics_bench"><img src="docs/src/_images/srb_multi_env.jpg" width="100%"></a>
 </p>
 
-<p align="left">
-  <a href="https://discord.gg/sSVccwVZ"><img alt="Discord" src="https://dcbadge.limes.pink/api/server/sSVccwVZ?style=flat&theme=discord&compact=true"></a>
-  &nbsp;
-  <a href="https://github.com/AndrejOrsula/space_robotics_bench/actions/workflows/rust.yml"><img alt="Rust" src="https://github.com/AndrejOrsula/space_robotics_bench/actions/workflows/rust.yml/badge.svg"></a>
-  <a href="https://github.com/AndrejOrsula/space_robotics_bench/actions/workflows/python.yml"><img alt="Python" src="https://github.com/AndrejOrsula/space_robotics_bench/actions/workflows/python.yml/badge.svg"></a>
-  <a href="https://github.com/AndrejOrsula/space_robotics_bench/actions/workflows/docker.yml"><img alt="Docker" src="https://github.com/AndrejOrsula/space_robotics_bench/actions/workflows/docker.yml/badge.svg"></a>
-  <a href="https://github.com/AndrejOrsula/space_robotics_bench/actions/workflows/docs.yml"><img alt="Docs" src="https://github.com/AndrejOrsula/space_robotics_bench/actions/workflows/docs.yml/badge.svg"></a>
-</p>
+[![Discord](https://dcbadge.limes.pink/api/server/p9gZAPWa65?style=flat&theme=discord&compact=true)](https://discord.gg/p9gZAPWa65)
+[![Rust](https://github.com/AndrejOrsula/space_robotics_bench/actions/workflows/rust.yml/badge.svg)](https://github.com/AndrejOrsula/space_robotics_bench/actions/workflows/rust.yml)
+[![Python](https://github.com/AndrejOrsula/space_robotics_bench/actions/workflows/python.yml/badge.svg)](https://github.com/AndrejOrsula/space_robotics_bench/actions/workflows/python.yml)
+[![Docker](https://github.com/AndrejOrsula/space_robotics_bench/actions/workflows/docker.yml/badge.svg)](https://github.com/AndrejOrsula/space_robotics_bench/actions/workflows/docker.yml)
+[![Docs](https://github.com/AndrejOrsula/space_robotics_bench/actions/workflows/docs.yml/badge.svg)](https://github.com/AndrejOrsula/space_robotics_bench/actions/workflows/docs.yml)
 
 The **Space Robotics Bench** aims to be a comprehensive collection of environments and tasks for robotics research in the challenging domain of space. The benchmark covers a wide range of applications and scenarios while providing a unified framework for experimenting with new tasks. Although the primary focus is on the application of robot learning techniques, the benchmark is designed to be flexible and extensible to accommodate a variety of research directions.
 
@@ -27,4 +24,4 @@ This project is dual-licensed under either the [MIT](LICENSE-MIT) or [Apache 2.0
 
 All assets created by contributors of this repository and those generated from the included procedural pipelines are licensed under the [CC0 1.0 Universal](https://github.com/AndrejOrsula/srb_assets/blob/main/LICENSE-CC0) license. Some assets are based on modified third-party resources, which might require you to give appropriate credit to the original author. Please review [`srb_assets` repository](https://github.com/AndrejOrsula/srb_assets) for more information.
 
-<a href="https://creativecommons.org/publicdomain/zero/1.0"><img alt="CC0 1.0 Universal" src="https://licensebuttons.net/l/zero/1.0/88x31.png" width="88" height="31"></a>
+[![CC0 1.0 Universal](https://licensebuttons.net/l/zero/1.0/88x31.png)](https://creativecommons.org/publicdomain/zero/1.0)