Update README.md

README.md

@@ -1,11 +1,10 @@
 ***After generating all VCF files you want to include in the panel,***
-
 ***you can use bcftools-merge to merge them into a single Panel of Normal VCF.***
 #### Usage
-```shell
+```bash
 # Enter the Choppy work environment
 open-choppy-env
-# APP `bcftools-merge` should be installed for the first time
+# App `bcftools-merge` should be installed for the first time
 choppy install YaqingLiu/bcftools-merge
 # Create input file `samples.json`
 touch samples.json