DOC: Make hex logo smaller

README.md

@@ -6,13 +6,13 @@
 [![Build Status](https://github.com/has2k1/plotnine/workflows/build/badge.svg?branch=main)](https://github.com/has2k1/plotnine/actions?query=branch%3Amain+workflow%3A%22build%22)
 [![Coverage](https://codecov.io/github/has2k1/plotnine/coverage.svg?branch=main)](https://codecov.io/github/has2k1/plotnine?branch=main)
 
+<img width="20%" align="right" src="https://github.com/has2k1/plotnine/blob/logos/doc/images/logo-512.png?raw=true">
+
 plotnine is an implementation of a *grammar of graphics* in Python
 based on [ggplot2](https://github.com/tidyverse/ggplot2).
 The grammar allows you to compose plots by explicitly mapping variables in a
 dataframe to the visual characteristics (position, color, size etc.) of objects that make up the plot.
 
-<img width="33%" align="right" src="https://github.com/has2k1/plotnine/blob/logos/doc/images/logo-512.png?raw=true">
-
 Plotting with a *grammar of graphics* is powerful. Custom (and otherwise
 complex) plots are easy to think about and build incrementally, while the
 simple plots remain simple to create.