fix: correct speedup plot image path in README (#333)

Co-authored-by: Orion Cohen <[email protected]>

Author: jQuinRivero

README.md

@@ -93,7 +93,7 @@ print(relaxed_state.energy)
 
 TorchSim achieves up to 100x speedup compared to ASE with popular MLIPs.
 
-<img src="/docs/_static/speedup_plot.svg" alt="Speedup comparison" width="100%">
+<img src="https://raw.githubusercontent.com/TorchSim/torch-sim/main/docs/_static/speedup_plot.svg" alt="Speedup comparison" width="100%">
 
 This figure compares the time per atom of ASE and `torch_sim`. Time per atom is defined
 as the number of atoms / total time. While ASE can only run a single system of `n_atoms`