promote the use of Python 3.8 instead of 3.7

README.md

@@ -66,7 +66,7 @@ conda install nf-core
 Alternatively, you can create a new environment with both nf-core/tools and nextflow:
 
 ```bash
-conda create --name nf-core python=3.7 nf-core nextflow
+conda create --name nf-core python=3.8 nf-core nextflow
 conda activate nf-core
 ```