Make emmet.syntaxProfiles configuration item to support custom language Id

[lost-bytes-x]

Make emmet.syntaxProfiles configuration item to support custom language Id. For example:

Previously, if you wanted to modify the final output of Markdown Emmet, you had to configure it like this:

...
  "emmet.includeLanguages": { "markdown": "html" },
  "emmet.syntaxProfiles": {
    "html": {
      "tag_nl": false,
      "tag_nl_leaf": false
    }
  },
...

Since it modifies the html configuration, the output for the HTML language will also be affected. With this commit, it is now supported:

...
  "emmet.includeLanguages": { "markdown": "html" },
  "emmet.syntaxProfiles": {
    "markdown": {
      "tag_nl": false,
      "tag_nl_leaf": false
    }
  },
...

This way, only the markdown configuration is modified, and the HTML language configuration will not be affected.

[lost-bytes-x]

@rzhao271 Looking forward to your approval 😀