feat(src/assets/icons/screenshot): add monitor, region, and window SVG icons for screenshot

src/assets/icons/screenshot/monitor.svg

@@ -0,0 +1,5 @@
+<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" width="32" height="32">
+    <rect x="6" y="8" width="20" height="3" rx="1.5" fill="#ffffff" opacity="0.5"/>
+    <rect width="20" height="16" x="6" y="8" rx="2.5" ry="2.5" fill="none" stroke="#fff" stroke-width="1" />
+    <rect x="11" y="21" width="10" height="2" rx="1" ry="1" fill="#ffffff" opacity="0.5"/>
+</svg>

src/assets/icons/screenshot/region.svg

@@ -0,0 +1,3 @@
+<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" width="32" height="32">
+    <rect width="20" height="16" x="6" y="8" rx="2" ry="2" fill="none" stroke="#fff" stroke-dasharray="2 2" stroke-width="1" />
+</svg>

src/assets/icons/screenshot/window.svg

@@ -0,0 +1,7 @@
+<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" width="32" height="32">
+    <rect x="6" y="8" width="20" height="4" rx="1.0" fill="#ffffff"/>
+    <rect width="20" height="16" x="6" y="8" rx="2" ry="2" fill="none" stroke="#fff" stroke-width="1" />
+    <circle cx="8" cy="10" r="1" fill="#222" />
+    <circle cx="11" cy="10" r="1" fill="#222" />
+    <circle cx="14" cy="10" r="1" fill="#222" />
+</svg>