Enhancement: Extend the i18n/language button

[wottpal]

Current Behavior:
In a multilingual setup, I can auto-create md|mdx files in all other defined languages. After these are created, the button is basically useless.

Desired/Extended Behavior:
In our case it's a pretty common scenario that we are toggling between different locales of one and the same page. I imagine the current i18n-button being extended to handle both cases:

• If files in other locales are not yet existent, create them.
• If files in other locales are existent, open/toggle them.

The only small detail (UX consideration) here is: What if there are more than two locales? – I would suggest in this case, a dropdown/menu (QuickPick) opens that lets the user decide which locale to create and/or open.

[wottpal]

@estruyf Could you give me some hints where to stark looking into if I want to try to tackle this myself in a PR? :)

[estruyf]

To start working on this, you will have to look at the following things:

• Registration of the i18n action in the editor title bar -

  vscode-front-matter/package.json

  Lines 2450 to 2454 in 3d8c550

  	{
  	"command": "frontMatter.i18n.create",
  	"group": "navigation@-127",
  	"when": "frontMatter:file:isValid && frontMatter:i18n:enabled"
  	},

• The frontMatter.i18n.create command:

  vscode-front-matter/src/commands/i18n.ts

  Line 260 in 3d8c550

  private static async create(fileUri?: Uri | string) {

Let me know if you need help on this one.