add logo to README.md

Author: abelcarreras

README.md

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 [![Test and Deploy](https://github.com/abelcarreras/posym/actions/workflows/python-publish.yml/badge.svg?branch=master)](https://github.com/abelcarreras/posym/actions/workflows/python-publish.yml)
 [![DOI](https://zenodo.org/badge/DOI/10.5281/zenodo.7261326.svg)](https://doi.org/10.5281/zenodo.7261326)
 
-<table>
-<tr>
-<td style="vertical-align: middle;"><img src="posym_logo.png" alt="Logo" width="70"></td>
-<td style="vertical-align: middle;"><h1>PoSym</h1></td>
-</tr>
-</table>
+<h1>
+  <img src="posym_logo.png" alt="Logo" width="20" style="vertical-align: middle;">
+  PoSym
+</h1>
 
 A point symmetry analysis tool written in python designed for theoretical chemistry.
 This tool makes use of continuous symmetry measures (CSM) to provide a robust implementation