add linter configuration

.eslintrc.yml

@@ -0,0 +1,17 @@
+env:
+  browser: true
+  jquery: true
+extends: 'eslint:recommended'
+rules:
+  indent:
+    - error
+    - 2
+  linebreak-style:
+    - error
+    - unix
+  quotes:
+    - error
+    - single
+  semi:
+    - error
+    - always

.slim-lint.yml

@@ -0,0 +1,3 @@
+linters:
+  LineLength:
+    max: 140