New filter - Block change-detection if text matches - for example, block change-detection while the text "out of stock" is on the page, know when the text is no longer on the page (#698)

changedetectionio/templates/edit.html

@@ -199,6 +199,22 @@ nav
                         </span>
                     </div>
                 </fieldset>
+                <fieldset>
+                    <div class="pure-control-group">
+                        {{ render_field(form.text_should_not_be_present, rows=5, placeholder="For example: Out of stock
+Sold out
+Not in stock
+Unavailable") }}
+                        <span class="pure-form-message-inline">
+                            <ul>
+                                <li>Block change-detection while this text is on the page, all text and regex are tested <i>case-insensitive</i>, good for waiting for when a product is available again</li>
+                                <li>Block text is processed from the result-text that comes out of any CSS/JSON Filters for this watch</li>
+                                <li>All lines here must not exist (think of each line as "OR")</li>
+                                <li>Note: Wrap in forward slash / to use regex  example: <code>/foo\d/</code></li>
+                            </ul>
+                        </span>
+                    </div>
+                </fieldset>
                 <fieldset>
                     <div class="pure-control-group">
                         {{ render_field(form.extract_text, rows=5, placeholder="\d+ online") }}