build: configure flutter launcher icons

- Added launcher icon config
- Configured android icons
- Configured web icons

Author: fulleni

flutter_launcher_icons.yaml

@@ -0,0 +1,22 @@
+flutter_launcher_icons:
+  image_path: "assets/icon/headlines_toolkit.png"
+
+  android: "launcher_icon"
+  # image_path_android: "assets/icon/headlines_toolkit.png"
+  min_sdk_android: 21 # android min sdk min:16, default 21
+  # adaptive_icon_background: "assets/icon/background.png"
+  # adaptive_icon_foreground: "assets/icon/foreground.png"
+  # adaptive_icon_monochrome: "assets/icon/monochrome.png"
+
+  ios: false
+  # image_path_ios: "assets/icon/headlines_toolkit.png"
+  remove_alpha_channel_ios: true
+  # image_path_ios_dark_transparent: "assets/icon/icon_dark.png"
+  # image_path_ios_tinted_grayscale: "assets/icon/icon_tinted.png"
+  # desaturate_tinted_to_grayscale_ios: true
+
+  web:
+    generate: true
+    # image_path: "assets/icon/headlines_toolkit.png"
+    background_color: "#fcfcfc"
+    theme_color: "#fcfcfc"