chore: add prettier (#286)

Adds prettier and the associated formatting changes.

This also updates the editor config to match that of chai itself.

Author: 43081j

.editorconfig

@@ -6,7 +6,4 @@ insert_final_newline = true
 trim_trailing_whitespace = true
 charset = utf-8
 indent_style = space
-indent_size = 4
-
-[.eslintrc.json]
 indent_size = 2

.prettierrc.json

@@ -0,0 +1,10 @@
+{
+  "bracketSpacing": false,
+  "printWidth": 80,
+  "semi": true,
+  "singleQuote": true,
+  "tabWidth": 2,
+  "trailingComma": "none",
+  "useTabs": false,
+  "arrowParens": "always"
+}