improve link preview images

SessionMessagingKit/Sending & Receiving/Link Previews/OWSLinkPreview.swift

@@ -695,14 +695,6 @@ public class OWSLinkPreview: MTLModel {
         guard let imageMimeType = MIMETypeUtil.mimeType(forFileExtension: imageFileExtension) else {
             return nil
         }
-        let kValidMimeTypes = [
-            OWSMimeTypeImagePng,
-            OWSMimeTypeImageJpeg,
-            OWSMimeTypeImageGif,
-        ]
-        guard kValidMimeTypes.contains(imageMimeType) else {
-            return nil
-        }
         return imageMimeType
     }
 

SessionUtilitiesKit/Media/MIMETypeUtil.m

@@ -85,7 +85,8 @@ NSString *const kSyncMessageFileExtension = @"bin";
             @"image/x-tiff" : @"tif",
             @"image/bmp" : @"bmp",
             @"image/x-windows-bmp" : @"bmp",
-            @"image/gif" : @"gif"
+            @"image/gif" : @"gif",
+            @"image/x-icon": @"ico"
         };
     });
     return result;

SessionUtilitiesKit/Media/NSData+Image.m

@@ -79,10 +79,6 @@ typedef NS_ENUM(NSInteger, ImageFormat) {
         return NO;
     }
 
-    if (![data ows_isValidImageWithMimeType:mimeType]) {
-        return NO;
-    }
-
     if (![self ows_hasValidImageDimensionsAtPath:filePath isAnimated:isAnimated]) {
         return NO;
     }