offer using Alt key as Meta key (fixes #316)

terminus-terminal/src/components/terminalSettingsTab.component.pug

@@ -358,3 +358,9 @@ h3.mt-3.mb-3 Behaviour
         (ngModelChange)='config.save()',
         text='Copy on select',
     )
+    
+    checkbox(
+        [(ngModel)]='config.store.terminal.altIsMeta',
+        (ngModelChange)='config.save()',
+        text='Use Alt key as the Meta key',
+    )

terminus-terminal/src/components/terminalTab.component.ts

@@ -371,6 +371,7 @@ export class TerminalTabComponent extends BaseTabComponent {
         preferenceManager.set('ctrl-plus-minus-zero-zoom', false)
         preferenceManager.set('scrollbar-visible', this.hostApp.platform === Platform.macOS)
         preferenceManager.set('copy-on-select', config.terminal.copyOnSelect)
+        preferenceManager.set('alt-is-meta', config.terminal.altIsMeta)
         preferenceManager.set('alt-sends-what', 'browser-key')
         preferenceManager.set('alt-gr-mode', 'ctrl-alt')
         preferenceManager.set('pass-alt-number', true)

terminus-terminal/src/config.ts

@@ -16,6 +16,7 @@ export class TerminalConfigProvider extends ConfigProvider {
             rightClick: 'menu',
             copyOnSelect: false,
             workingDirectory: '',
+            altIsMeta: false,
             colorScheme: {
                 __nonStructural: true,
                 name: 'Material',