config:output:Allow multiple exclusions & wildcard

Covers the use case where needing to exclude more than 1 output but
still include all other displays.

e.g. I have 3 monitors: laptop + HD + 4K; and 3 bar types:
- The main bar is on the laptop. `output: "laptop-monitor-id"`
- The 4K has a specific waybar bar-1 configuration. `output: "4K-monitor-id"`
- I want all other displays (3rd HD monitor / any HDMI output when presenting)
  to have a plain bar: `output: ["!laptop-monitor-id", "!4k-monitor-id", "*"]`

man/waybar.5.scd.in

@@ -30,6 +30,7 @@ Also a minimal example configuration can be found on the at the bottom of this m
 *output* ++
 	typeof: string|array ++
 	Specifies on which screen this bar will be displayed. Exclamation mark(*!*) can be used to exclude specific output.
+	In an array, star '*\**' can be used at the end to accept all outputs, in case all previous entries are exclusions.
 
 *position* ++
 	typeof: string ++

src/config.cpp

@@ -124,9 +124,21 @@ bool isValidOutput(const Json::Value &config, const std::string &name,
                    const std::string &identifier) {
   if (config["output"].isArray()) {
     for (auto const &output_conf : config["output"]) {
-      if (output_conf.isString() &&
-          (output_conf.asString() == name || output_conf.asString() == identifier)) {
-        return true;
+      if (output_conf.isString()) {
+        auto config_output = output_conf.asString();
+        if (config_output.substr(0, 1) == "!") {
+          if (config_output.substr(1) == name || config_output.substr(1) == identifier) {
+            return false;
+          } else {
+            continue;
+          }
+        }
+        if (config_output == name || config_output == identifier) {
+          return true;
+        }
+        if (config_output.substr(0, 1) == "*") {
+          return true;
+        }
       }
     }
     return false;