Clearer documentation for relative path and wildcards in README.md

Is your enhancement related to a problem? Please describe.

It took me a bit to figure out how to use a relative path and wildcards in settings.json; I found the documentation in README.md unclear about this.

My working solution

"yaml.schemas": {
    "./path/to/schemas/project.json": [
        "/path/to/projects/**/*.yaml",
    ]
}

Describe the solution you would like

The README.md should contain clear instructions and an easy to understand example.

Additional context

Here is what I would add, after the On Mac/Linux with full path: sample code:

To provide a relative path,

• for the schema, specify it from the root folder starting with a dot: ./path/from/root/folder;
• for the yaml files, specify it from the root folder without the dot: /path/from/root/folder.
  You can use wildcards: in the example, any of the two paths would work with the file my_project.yaml.

"yaml.schemas": {
   "./path/to/schemas/project.json": [
       "/path/to/projects/subfolder/my_project.yaml",
       "/path/to/projects/**/*.yaml",
   ]
}

Please provide feedback on this change, and tell me if I should take care of a pull request.

Open README.md and find the section containing the “On Mac/Linux with full path” sample. Clarify relative schema and YAML paths and add the proposed wildcard example; done means the README explains the path rules and shows an understandable settings.json configuration.