Preserve image anchors during migration

[Mpdreamz]

The following error:

Error: `img-pre-refresh` does not exist in near-real-time.md.
   ┌─[/Users/mpdreamz/Projects/elasticsearch.md/docs/near-real-time.md]
   │
 7 │ Sitting between {{es}} and the disk is the filesystem cache. Documents in the in-memory indexing buffer ([Figure 1](near-real-time.md#img-pre-refresh)) are written to a new segment ([Figure 2](near-real-time.md#img-post-refresh)). The new segment is written to the filesystem cache first (which is cheap) and only later is it flushed to disk (which is expensive). However, after a file is in the cache, it can be opened and read just like any other file.

Is due to the fact we don't preserve image anchors during migration:

From near-real-time.md

:::{image} images/lucene-in-memory-buffer.png
:alt: A Lucene index with new documents in the in-memory buffer
:title: 
:::

We can preserve them by adding the :name: property

:::{image} images/lucene-in-memory-buffer.png
:alt: A Lucene index with new documents in the in-memory buffer
:title: 
:name: img-pre-refresh
:::