Add API reference documentation for projection

[seesharprun]

Adds the API reference documentation for projection. Includes the following files:

• api-reference/operators/projection/$meta.md
• api-reference/operators/projection/index.md

---

Depends on #4

[AvijitkGupta]

We seem to be missing additional files under this category.

[seesharprun]

@AvijitkGupta, I just looked at the projection category and it appears you have articles multiple times in the TOC on Microsoft Learn:

But, if you look at the actual folder on Learn:

There's only one article. The other "links" are to articles from other categories:

	File
$	operators/array-update/$.md
$elemMatch	operators/array-query/$elemmatch.md
$meta	operators/projection/$meta.md
$slice	operators/array-expression/$slice.md