Improve yarn detection

Used the same detection as webpacker.
https://github.com/rails/webpacker/blob/9d29ddd14c2cbe94f4aad154a92f4a2a40b498fd/lib/tasks/webpacker/check_yarn.rake#L4-L22

Author: johansmitsnl

lib/generators/hyperloop/install_bootstrap_generator.rb

@@ -7,7 +7,12 @@ class  InstallBootstrapGenerator < Rails::Generators::Base
     class_option 'no-build', type: :boolean
 
     def insure_yarn_loaded
-      raise Thor::Error.new("please insure the yarn command is available") if `command -v yarn`.blank?
+      begin
+        yarn_version = `yarn --version`
+        raise Errno::ENOENT if yarn_version.blank?
+      rescue Errno::ENOENT
+        raise Thor::Error.new("please insure the yarn command is available if using webpacker")
+      end
     end
 
     def add_to_manifests

lib/generators/hyperloop/install_generator.rb

@@ -8,7 +8,12 @@ class InstallGenerator < Rails::Generators::Base
 
     def insure_yarn_loaded
       return if skip_webpack?
-      raise Thor::Error.new("please insure the yarn command is available if using webpacker") if `command -v yarn`.blank?
+      begin
+        yarn_version = `yarn --version`
+        raise Errno::ENOENT if yarn_version.blank?
+      rescue Errno::ENOENT
+        raise Thor::Error.new("please insure the yarn command is available if using webpacker")
+      end
     end
 
     def inject_react_file_js

lib/generators/hyperloop/install_mui_generator.rb

@@ -7,7 +7,12 @@ class  InstallMuiGenerator < Rails::Generators::Base
     class_option 'no-build', type: :boolean
 
     def insure_yarn_loaded
-      raise Thor::Error.new("please insure the yarn command is available") if `command -v yarn`.blank?
+      begin
+        yarn_version = `yarn --version`
+        raise Errno::ENOENT if yarn_version.blank?
+      rescue Errno::ENOENT
+        raise Thor::Error.new("please insure the yarn command is available if using webpacker")
+      end
     end
 
     def add_to_manifests