change logo source within README.md to use locallly sourced file in docs rather than the hosted version

Author: harryswift01

README.md

@@ -11,7 +11,7 @@ CodeEntropy
 CodeEntropy is a Python package for computing the configurational entropy of macromolecular systems using forces sampled from molecular dynamics (MD) simulations. It implements the multiscale cell correlation method to provide accurate and efficient entropy estimates, supporting a wide range of applications in molecular simulation and statistical mechanics.
 
 <p align="center">
-<img src="https://github.com/CCPBioSim/branding/blob/fbf562b1f5a9bf34440d0a537548591bad0bd206/logos/biosim-codeentropy_logo_grey.png" alt="CodeEntropy logo" width="300"/>
+<img src="docs/images/biosim-codeentropy_logo_grey.svg" alt="CodeEntropy logo" width="300"/>
 </p>
 
 See [CodeEntropy’s documentation](https://codeentropy.readthedocs.io/en/latest/) for more information.