adding software blitter base

src/soft/device/Blitter.zig

@@ -0,0 +1,27 @@
+const std = @import("std");
+const vk = @import("vulkan");
+const base = @import("base");
+
+pub const SoftImage = @import("../SoftImage.zig");
+pub const SoftImageView = @import("../SoftImageView.zig");
+
+const Self = @This();
+
+blit_mutex: std.Thread.Mutex,
+
+pub const init: Self = .{
+    .blit_mutex = .{},
+};
+
+pub fn clear(self: *Self, pixel: *const anyopaque, format: vk.Format, dest: *SoftImage, view_format: vk.Format, range: vk.ImageSubresourceRange, area: ?vk.Rect2D) void {
+    const dst_format = base.Image.formatFromAspect(view_format, range.aspect_mask);
+    if (dst_format == .undefined) {
+        return;
+    }
+
+    _ = self;
+    _ = pixel;
+    _ = format;
+    _ = dest;
+    _ = area;
+}