Add DOI for Oblapenko et al. (#114)

* add preprint from Jesse

* add doi for Oblapenko et al.

Author: andrewwinters5000

index.md

@@ -334,6 +334,7 @@ listed above. Author names of Trixi.jl's main developers are in *italics*.
 * Oblapenko, Tarnovskiy, Ertl, Torrilhon,
   **Entropy-stable fluxes for high-order Discontinuous Galerkin simulations of high-enthalpy flows**, 2024.\\
   [![arXiv:2411.13168](https://img.shields.io/badge/arXiv-2411.13168-yellow)](https://arxiv.org/abs/2411.13168)
+  [![doi:10.1007/978-3-032-11115-9_36](https://zenodo.org/badge/doi/10.1007/978-3-032-11115-9_36.svg)](https://doi.org/10.1007/978-3-032-11115-9_36)
   [![reproduce me!](https://img.shields.io/badge/reproduce-me!-brightgreen)](https://github.com/knstmrd/paper_ec_trixi_chem)
 
 * Bender, Öffner,