docs: Update instructions for running developer scripts (#80)

### Motivation

The documentation has an example of running one of the developer scripts in the `scripts/` directory. The scripts are not executable, so need explicitly running with `bash`.

### Modifications

Update docs to reflect the need to run the scripts with `bash`.

CONTRIBUTORS.txt

@@ -19,4 +19,4 @@ needs to be listed here.
 
 **Updating this list**
 
-Please do not edit this file manually. It is generated using `./scripts/generate-contributors-list.sh`. If a name is misspelled or appearing multiple times: add an entry in `./.mailmap`
+Please do not edit this file manually. It is generated using `bash ./scripts/generate-contributors-list.sh`. If a name is misspelled or appearing multiple times: add an entry in `./.mailmap`

scripts/generate-contributors-list.sh

@@ -48,5 +48,5 @@ cat > "$here/../CONTRIBUTORS.txt" <<- EOF
 
 	**Updating this list**
 
-	Please do not edit this file manually. It is generated using \`./scripts/generate-contributors-list.sh\`. If a name is misspelled or appearing multiple times: add an entry in \`./.mailmap\`
+	Please do not edit this file manually. It is generated using \`bash ./scripts/generate-contributors-list.sh\`. If a name is misspelled or appearing multiple times: add an entry in \`./.mailmap\`
 EOF