New lightmode and darkmode themes with UI revamp.

Signed-off-by: Adam Treat <treat.adam@gmail.com>

gpt4all-chat/qml/MySettingsButton.qml

@@ -0,0 +1,38 @@
+import QtCore
+import QtQuick
+import QtQuick.Controls
+import QtQuick.Controls.Basic
+import mysettings
+
+Button {
+    id: myButton
+    padding: 10
+    rightPadding: 18
+    leftPadding: 18
+    property color textColor: MySettings.chatTheme === "Dark" ? theme.green800 : theme.green600
+    property color mutedTextColor: textColor
+    property color backgroundColor: MySettings.chatTheme === "Dark" ? theme.green400 : theme.green200
+    property color backgroundColorHovered: theme.green300
+    property real  borderWidth: 0
+    property color borderColor: "transparent"
+    property real fontPixelSize: theme.fontSizeLarge
+
+    contentItem: Text {
+        text: myButton.text
+        horizontalAlignment: Text.AlignHCenter
+        color: myButton.enabled ? textColor : mutedTextColor
+        font.pixelSize: fontPixelSize
+        font.bold: true
+        Accessible.role: Accessible.Button
+        Accessible.name: text
+    }
+    background: Rectangle {
+        radius: 10
+        border.width: borderWidth
+        border.color: borderColor
+        color: myButton.hovered ? backgroundColorHovered : backgroundColor
+    }
+    Accessible.role: Accessible.Button
+    Accessible.name: text
+    ToolTip.delay: Qt.styleHints.mousePressAndHoldInterval
+}