Highlight custom @tags in jsdoc comments

[mjbvz]

From microsoft/vscode#63893

TS and JS Grammar Extension version: 0.0.47 / latest

Code
For comments that use custom jsdoc tags such as:

/**
 * @privateRemarks 
 * Bla bla bla.
 */
const foo = 1

Highlight @privateRemarks differently than a regular comment conent . We already handle known jsdoc tags like @abstract; This request is to also highlight custom tags