fix(docs): typo in install.md

docs/user-guide/install.md

@@ -68,7 +68,7 @@ You will then be able to enable nixvim through `programs.nixvim.enable = true`,
 options as `programs.nixvim.<path>.<to>.<option> = <value>`.
 
 When you use nixvim as a module, an additional module argument is passed on allowing you to peek through the configuration with `hmConfig`, `nixosConfig`, and `darwinConfig` for home-manager, NixOS, and nix-darwin respectively.
-This is useful is you use nixvim both as part of an environment and as standalone.
+This is useful if you use nixvim both as part of an environment and standalone.
 
 For more platform-specific options and information, see [Nixvim Platforms](../platforms/index.md).