feat: save config if no config file was found

`patch-hub` relies on configurations to work properly. These can be
determined by (1) default values, (2) configuration file, and (3) env
variables.

In case there is no configuration file detected, save the default one.

[Maintainers edits]
- Add TODO comment for better handle error when saving config file.
- Add commit message body.

Signed-off-by: OJarrisonn <j.h.m.t.v.10@gmail.com>
Reviewed-by: David Tadokoro <davidbtadokoro@usp.br>
Signed-off-by: David Tadokoro <davidbtadokoro@usp.br>

src/app/config.rs

@@ -88,11 +88,12 @@ impl Config {
     }
 
     pub fn build() -> Self {
-        let mut config = Self::default();
-
-        if let Some(config_from_file) = Self::detect_patch_hub_config_file() {
-            config = config_from_file;
-        }
+        let mut config = Self::detect_patch_hub_config_file().unwrap_or_else(|| {
+            let config = Self::default();
+            // TODO: Better handle this error
+            let _ = config.save_patch_hub_config();
+            config
+        });
 
         config.override_with_env_vars();