Inform users about 16 color limit with WSL

This patch adds a warning that when using WSL we're limited to 16 colors. It took me about 4 hours debugging why it didn't work, and this patch hopefully prevents others from wasting 4 hours.

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

@@ -14,6 +14,10 @@ h3.mb-3 Shell
             [ngValue]='shell.id'
         ) {{shell.name}}
 
+.alert.alert-info.d-flex.align-items-center(*ngIf='config.store.terminal.shell.startsWith("wsl")')
+    .mr-auto WSL terminal only supports 16 colors until ConPTY is implemented in node-pty
+    button.btn.btn-secondary((click)='openConPtyInfo()') More Information
+
 .form-line(*ngIf='config.store.terminal.shell == "custom"')
     .header
         .title Custom shell

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

@@ -30,6 +30,10 @@ export class ShellSettingsTabComponent {
         this.shells = (await Promise.all(this.config.enabledServices(this.shellProviders).map(x => x.provide()))).reduce((a, b) => a.concat(b))
     }
 
+    openConPtyInfo() {
+        this.electron.shell.openExternal('https://github.com/Microsoft/node-pty/issues/216')
+    }
+
     ngOnDestroy () {
         this.configSubscription.unsubscribe()
     }