feat: support supplementary environment variables for hooks in App (#5916)

* feat: Implement launcher supplementary environmental variables, and env var substitution in hooks

* lint fix, prettier reformat

* descriptions added for each environment variable for hook settings

* alphabetize language keys

---------

Co-authored-by: Prospector <6166773+Prospector@users.noreply.github.com>

apps/app-frontend/src/components/ui/settings/instances/DefaultInstanceSettings.vue

@@ -116,6 +116,35 @@ const messages = defineMessages({
 		id: 'app.settings.default-instance-options.post-exit-hook.description',
 		defaultMessage: 'Runs after the game closes.',
 	},
+	hookVariablesDescription: {
+		id: 'instance.settings.tabs.hooks.variables.description',
+		defaultMessage:
+			'Hooks run in the working directory of the instance, with the following variables:',
+	},
+	instanceNameDescription: {
+		id: 'instance.settings.tabs.hooks.variables.inst-name.description',
+		defaultMessage: '$INST_NAME: The name of the instance',
+	},
+	instanceIdDescription: {
+		id: 'instance.settings.tabs.hooks.variables.inst-id.description',
+		defaultMessage: "$INST_ID: The name of the instance's folder",
+	},
+	instanceDirDescription: {
+		id: 'instance.settings.tabs.hooks.variables.inst-dir.description',
+		defaultMessage: "$INST_DIR: The absolute path to the instance's folder",
+	},
+	instanceMcDirDescription: {
+		id: 'instance.settings.tabs.hooks.variables.inst-mc-dir.description',
+		defaultMessage: '$INST_MC_DIR: An alias for $INST_DIR',
+	},
+	instanceJavaDescription: {
+		id: 'instance.settings.tabs.hooks.variables.inst-java.description',
+		defaultMessage: '$INST_JAVA: The absolute path to the java binary',
+	},
+	instanceJavaArgsDescription: {
+		id: 'instance.settings.tabs.hooks.variables.inst-java-args.description',
+		defaultMessage: '$INST_JAVA_ARGS: The JVM Arguments provided to the game',
+	},
 })
 
 const fetchSettings = await get()
@@ -328,6 +357,18 @@ watch(
 					{{ formatMessage(messages.postExitHookDescription) }}
 				</p>
 			</div>
+
+			<div class="m-0 leading-tight">
+				{{ formatMessage(messages.hookVariablesDescription) }}
+				<ul>
+					<li>{{ formatMessage(messages.instanceNameDescription) }}</li>
+					<li>{{ formatMessage(messages.instanceIdDescription) }}</li>
+					<li>{{ formatMessage(messages.instanceDirDescription) }}</li>
+					<li>{{ formatMessage(messages.instanceMcDirDescription) }}</li>
+					<li>{{ formatMessage(messages.instanceJavaDescription) }}</li>
+					<li>{{ formatMessage(messages.instanceJavaArgsDescription) }}</li>
+				</ul>
+			</div>
 		</div>
 	</div>
 </template>