add(view): View type for composing view modules

src/event.zig

@@ -12,6 +12,7 @@ pub const Error = struct {
 };
 
 // System events available to every application.
+// TODO: should this also already include the .view enum option?
 pub const SystemEvent = union(enum) {
     quit,
     err: Error,
@@ -21,6 +22,7 @@ pub const SystemEvent = union(enum) {
 };
 
 pub fn mergeTaggedUnions(comptime A: type, comptime B: type) type {
+    // TODO: should this expect one of the unions to contain the .view value option with its corresponding associated type?
     if (!isTaggedUnion(A) or !isTaggedUnion(B)) {
         @compileError("Both types for merging tagged unions need to be of type `union(enum)`.");
     }