JSDoc: add documentation for class @property declarations

[Morfent]

I noticed @property declarations appear to be supported, but are not
documented in the wiki.

[msftclas]

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[DanielRosenwasser]

I started fixing up the document, but I realized that the @property annotations were not actually working; these only seem to work because you're assigning fields in the constructor.

For example, in the following:

/**
 * @property {string} name
 */
class Foo {
    constructor() {
        this.name = 100;
    }
}

new Foo().name

TypeScript currently thinks the type of name is number.

[mhegazy]

this should be tracked by microsoft/TypeScript#15715