MetaData in header of GeoJSON - geojson

Question

Would it break most readers (and violate the spec) if I added some meta-data at the top of a GeoJSON file (or packet).
I looked at: https://gis.stackexchange.com/questions/96158/metadata-and-geojson
But I am not clear if that answered my question here.
For example, can an add more properties to the CRS object, other than "name", "properties" to get some extended meta-data, rather than putting it on each feature?

Answer 1

The geojson specs section 6.1 state (https://www.rfc-editor.org/rfc/rfc7946):
6.1. Foreign Members
Members not described in this specification ("foreign members") MAY be
used in a GeoJSON document. Note that support for foreign members can
vary across implementations, and no normative processing model for
foreign members is defined. Accordingly, implementations that rely
too heavily on the use of foreign members might experience reduced
interoperability with other implementations.
For example, in the (abridged) Feature object shown below
{
"type": "Feature",
"id": "f1",
"geometry": {...},
"properties": {...},
"title": "Example Feature" }
the name/value pair of "title": "Example Feature" is a foreign member.
When the value of a foreign member is an object, all the descendant
members of that object are themselves foreign members.
GeoJSON semantics do not apply to foreign members and their descendants, regardless of their names and values. For example, in
the (abridged) Feature object below
{
"type": "Feature",
"id": "f2",
"geometry": {...},
"properties": {...},
"centerline": {
"type": "LineString",
"coordinates": [
[-170, 10],
[170, 11]
]
} }
the "centerline" member is not a GeoJSON Geometry object.

Answer 2

I don't know about whether it violates specs, but I did something similar and it did not break the reader.
For example, I had a GeoJSON file with 10 features, and wanted to add a time stamp to it. I accomplished this with Javascript (Node.js):
var json_in = require('/path/to/file/input.json');
var timei = ("2016-10-31 12Z");
var jsonfile = require('jsonfile');
var file = '/path/to/file/output.json';
jsonfile.writeFile(file, json_in, function (err) {
console.error(err)
})
I then mapped out the features on http://geojson.io and confirmed that everything looked right.
FYI You can get the jsonfile package (makes I/O much smoother) here:
https://github.com/jprichardson/node-jsonfile