make rg use smart case

this makes the search case insensitive by default but case sensitive
when uppercase letters are used. I'd like something similar to vim where
you can preface the query with `\C` to force case sensitivity but afaict
rg doesnt have this, maybe we just do it ourselves?

src/ripgrep.zig

@@ -120,6 +120,7 @@ const Process = struct {
             // "--line-buffered",
             "--fixed-strings",
             "--json",
+            "--smart-case",
             self.query,
         });
         self.sp = tp.subprocess.init(self.allocator, args, module_name, self.stdin_behavior) catch |e| return tp.exit_error(e, @errorReturnTrace());