Add four spaces, not tabs.

ale_linters/fountain/proselint.vim

@@ -2,8 +2,8 @@
 " Description: proselint for Fountain files
 
 call ale#linter#Define('fountain', {
-\	'name': 'proselint',
-\	'executable': 'proselint',
-\	'command': 'proselint %t',
-\	'callback': 'ale#handlers#unix#HandleAsWarning',
+\    'name': 'proselint',
+\    'executable': 'proselint',
+\    'command': 'proselint %t',
+\    'callback': 'ale#handlers#unix#HandleAsWarning',
 \})