Merge pull request #2828 from OSGeo/backport-2826-to-8.1

[Backport 8.1] Doc: projjson.rst: update to PROJJSON v0.3

docs/source/specifications/projjson.rst

@@ -13,17 +13,18 @@ the same as WKT2:2019.
 
 PROJJSON is available as input and output of PROJ since PROJ 6.2.
 
-The current version is 0.2.
+The current version is 0.3.
 
 Schema
 ------
 
 A JSON schema of its grammar is available at
-https://proj.org/schemas/v0.2/projjson.schema.json
+https://proj.org/schemas/v0.3/projjson.schema.json
 
 History
 -------
 
+* v0.3: additional properties allowed in BoundCRS object (name, scope, area, bbox, usages, remarks, id, ids)
 * v0.2: addition of geoid_model in VerticalCRS object.
 * v0.1: initial version for PROJ 6.2