Add link to Laravel Framework validation rules/docs

Small QoL fix for adding variables to eggs:

References to "Laravel Framework validation rules" are now linked to the official Laravel 5.7 docs referring to the validation syntax.  Links are also set to open reference in a new tab/window.

Author: AusHick

resources/themes/pterodactyl/admin/eggs/variables.blade.php

@@ -81,7 +81,7 @@
                         <div class="form-group">
                             <label class="form-label">Input Rules</label>
                             <input type="text" name="rules" class="form-control" value="{{ $variable->rules }}" />
-                            <p class="text-muted small">These rules are defined using standard Laravel Framework validation rules.</p>
+                            <p class="text-muted small">These rules are defined using standard <a href="https://laravel.com/docs/5.7/validation" target="_blank">Laravel Framework validation rules</a>.</p>
                         </div>
                     </div>
                     <div class="box-footer">
@@ -134,7 +134,7 @@
                     <div class="form-group">
                         <label class="control-label">Input Rules <span class="field-required"></span></label>
                         <input type="text" name="rules" class="form-control" value="{{ old('rules', 'required|string|max:20') }}" placeholder="required|string|max:20" />
-                        <p class="text-muted small">These rules are defined using standard Laravel Framework validation rules.</p>
+                        <p class="text-muted small">These rules are defined using standard <a href="https://laravel.com/docs/5.7/validation" target="_blank">Laravel Framework validation rules</a>.</p>
                     </div>
                 </div>
                 <div class="modal-footer">