Added fields_for example with inline errors to the README.md

Fixes #656

Author: donv

README.md

@@ -1423,6 +1423,9 @@ error will be displayed below the field. Here's an example:
 ```erb
 <%= bootstrap_form_for(@user_with_error) do |f| %>
   <%= f.email_field :email %>
+  <%= f.fields_for :address do |af| %>
+    <%= af.text_field :street %>
+  <% end %>
 <% end %>
 ```
 
@@ -1435,6 +1438,11 @@ Generated HTML:
     <input class="form-control is-invalid" id="user_email" name="user[email]" required="required" type="email" value="steve.example.com">
     <div class="invalid-feedback">is invalid</div>
   </div>
+  <div class="mb-3">
+    <label class="form-label" for="user_address_attributes_street">Street</label>
+    <input class="form-control is-invalid" id="user_address_attributes_street" name="user[address_attributes][street]" type="text" value="Bar">
+    <div class="invalid-feedback">is invalid</div>
+  </div>
 </form>
 ```
 

demo/app/controllers/bootstrap_controller.rb

@@ -16,17 +16,13 @@ def fragment
 
   def load_models
     @address = Address.new(id: 1, street: "Foo")
-    @collection = [
-      @address,
-      Address.new(id: 2, street: "Bar")
-    ]
-
+    @address_with_error = Address.new(id: 2, street: "Bar")
+    @address_with_error.errors.add(:street)
+    @collection = [@address, @address_with_error]
     @user = User.new email: "[email protected]"
-
-    @user_with_error = User.new email: "steve.example.com"
+    @user_with_error = User.new email: "steve.example.com", address: @address_with_error
     @user_with_error.errors.add(:email)
     @user_with_error.errors.add(:misc)
-
     @users = [@user]
   end
 end