feat(single-instance): Add semver compatibility check for Windows and Linux (#502)

* added semver compatibility check for Windows and Linux

* fixed formatting

* put semver feature behind a feature flag

* remove semver from root manifest

* linux compile error

* docs: Add mention for semver feature in readme

---------

Co-authored-by: FabianLars <fabianlars@fabianlars.de>

plugins/single-instance/src/lib.rs

@@ -10,6 +10,9 @@ mod platform_impl;
 #[path = "platform_impl/macos.rs"]
 mod platform_impl;
 
+#[cfg(feature = "semver")]
+mod semver_compat;
+
 pub(crate) type SingleInstanceCallback<R> =
     dyn FnMut(&AppHandle<R>, Vec<String>, String) + Send + Sync + 'static;