📝 update documentation (#4723)

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

docs/mkdocs/docs/api/basic_json/to_bson.md

@@ -15,7 +15,7 @@ so-called document).
 1. Returns a byte vector containing the BSON serialization.
 2. Writes the BSON serialization to an output adapter.
 
-The exact mapping and its limitations is described on a [dedicated page](../../features/binary_formats/bson.md).
+The exact mapping and its limitations are described on a [dedicated page](../../features/binary_formats/bson.md).
 
 ## Parameters
 
@@ -27,7 +27,7 @@ The exact mapping and its limitations is described on a [dedicated page](../../f
 
 ## Return value
 
-1. BSON serialization as byte vector
+1. BSON serialization as a byte vector
 2. (none)
 
 ## Exception safety