Support `_.json` as an alias of `meta.json`

[shuding]

When a directory grows, meta.json might get lost in the giant list of document pages... but meta.json has a special meaning and functionality in a Nextra project, it would be nice to simplify the name, and always make it the first file in the list. This change will improve the experience tremendously.

It might be not performant to read both meta files. So if possible, we can also deprecate the meta.json support.

[alii]

Perhaps _meta.json would be more apt being more descriptive of what we're looking at. Similar to _app & _document etc

[dimaMachina]

@shuding it can be done easily with new theme nextra config option - unstable_underscoreMeta 😅

[AmiteyeEmmanuel]

How can I add an icon to my _meta.json Nextra document page, like for example,

{ “Index” : { “title” : “Introduction” “Icon”: “fa fas Introduction” // Not recognized by Nextra }

please help out.