Allow directly reading web pages, even when SERP not enabled (#676)

### Overview
Khoj can now read website directly without needing to go through the search step first

### Details
- Parallelize simple webpage read and extractor
- Rename extract_content online results field to web pages
- Tweak prompts to extract information from webpages, online results
- Test select webpage as data source and extract web urls chat actors

- Render webpage read in chat response references on Web, Desktop apps
- Pass multiple webpages with their urls in online results context

- Support webpage command in chat API
- Add webpage chat command for read web pages requested by user
- Create chat actor for directly reading webpages based on user message

src/interface/desktop/chat.html

@@ -87,7 +87,7 @@
         function generateOnlineReference(reference, index) {
 
             // Generate HTML for Chat Reference
-            let title = reference.title;
+            let title = reference.title || reference.link;
             let link = reference.link;
             let snippet = reference.snippet;
             let question = reference.question;
@@ -191,6 +191,15 @@
                         referenceSection.appendChild(polishedReference);
                     }
                 }
+
+                if (onlineReference.webpages && onlineReference.webpages.length > 0) {
+                    numOnlineReferences += onlineReference.webpages.length;
+                    for (let index in onlineReference.webpages) {
+                        let reference = onlineReference.webpages[index];
+                        let polishedReference = generateOnlineReference(reference, index);
+                        referenceSection.appendChild(polishedReference);
+                    }
+                }
             }
 
             return numOnlineReferences;