Add txt and markdown files to attach feature. (#3135)

Signed-off-by: Adam Treat <treat.adam@gmail.com>
Signed-off-by: AT <manyoso@users.noreply.github.com>
Co-authored-by: Jared Van Bortel <jared@nomic.ai>

gpt4all-chat/qml/MyFileIcon.qml

@@ -0,0 +1,41 @@
+import QtCore
+import QtQuick
+import QtQuick.Controls
+import QtQuick.Controls.Basic
+import Qt5Compat.GraphicalEffects
+
+Item {
+    id: fileIcon
+    property real iconSize: 24
+    property string fileName: ""
+    implicitWidth: iconSize
+    implicitHeight: iconSize
+
+    Image {
+        id: fileImage
+        anchors.fill: parent
+        visible: false
+        sourceSize.width: iconSize
+        sourceSize.height: iconSize
+        mipmap: true
+        source: {
+            if (fileIcon.fileName.toLowerCase().endsWith(".txt"))
+                return "qrc:/gpt4all/icons/file-txt.svg"
+            else if (fileIcon.fileName.toLowerCase().endsWith(".pdf"))
+                return "qrc:/gpt4all/icons/file-pdf.svg"
+            else if (fileIcon.fileName.toLowerCase().endsWith(".md"))
+                return "qrc:/gpt4all/icons/file-md.svg"
+            else if (fileIcon.fileName.toLowerCase().endsWith(".xlsx"))
+                return "qrc:/gpt4all/icons/file-xls.svg"
+            else if (fileIcon.fileName.toLowerCase().endsWith(".docx"))
+                return "qrc:/gpt4all/icons/file-docx.svg"
+            else
+                return "qrc:/gpt4all/icons/file.svg"
+        }
+    }
+    ColorOverlay {
+        anchors.fill: fileImage
+        source: fileImage
+        color: theme.textColor
+    }
+}