Don't modify settings.json when adding debug configurations

[colin-grant-work]

What it does

Fixes #9712 by checking whether the file found is a default config file (settings.json) before modifying it when adding debug configurations.

How to test

1. In an otherwise empty folder, create a .theia folder and populate it with a settings.json that includes a `"launch" field. Something like this:

{
  "launch": {
    // Use IntelliSense to learn about possible attributes.
    // Hover to view descriptions of existing attributes.
    "version": "0.2.0",
    "configurations": []
  },
  "editor.fontSize": 20
}

2. Open that folder in Theia.
3. Open the debug view, open the dropdown and select 'Add configurations'
4. It should open your settings.json and put you in the middle of the array, but it should not remove your "editor.fontSize" setting.

Review checklist

• as an author, I have thoroughly tested my changes and carefully followed the review guidelines

Reminder for reviewers

• as a reviewer, I agree to behave in accordance with the review guidelines

Signed-off-by: Colin Grant [email protected]

[vince-fugnitto]

I confirmed that it fixes the reported issue #9712 👍