Add PRQL to SQL context menus to PRQL editor title

[RandomFractals]

This change would add direct access to the prqlSqlOutputPanel.open command to the open PRQL editor title menu and vscode title bar context menu.

Required package.json changes to the extension contributes config:

...
    "commands": [
      {
        "command": "prqlSqlOutputPanel.open",
        "title": "Open SQL Output Panel",
        "category": "PRQL",
        "icon": "$(database)"
      }
    ],
    "menus": {
      "editor/title": [
        {
          "command": "prqlSqlOutputPanel.open",
          "when": "resourceFilename =~ /.*(.prql)/",
          "group": "navigation"
        }
      ],
      "editor/title/context": [
        {
          "command": "prqlSqlOutputPanel.open",
          "when": "resourceFilename =~ /.*\\.(prql)/",
          "group": "navigation"
        }
      ]
    }
...

We can use the standard vscode $(database} icon to expose Open SQL Output Panel command in the top right corner of editor panel as depicted below:

[max-sixty]

I think this would be great!

[RandomFractals]

Closing this as it was merged into main branch as part of PR #40.

We might consider changing prqlSqlOutputPanel.open command and editor title menu icon from $(database) to $(open-preview) and use the database icon later on for selection of database to connect to and run generated SQL.

I'll expand more on it in #42.