doc: add docs for bson_append_iter(3)
doc: add docs for bson_append_iter(3)

rayyang2000/libbson,rcsanchez97/libbson,mongodbinc-interns/libbson,ajdavis/libbson,remicollet/libbson,derickr/libbson,Machyne/libbson,Machyne/libbson,Convey-Compliance/libbson,jqk6/libbson,remicollet/libbson,remicollet/libbson,Convey-Compliance/libbson,bjori/libbson,Machyne/libbson,paulmelnikow/libbson,ksuarz/libbson,jqk6/libbson,paulmelnikow/libbson,mongodbinc-interns/libbson,alexeyvo/libbson,ksuarz/libbson,Convey-Compliance/libbson,mongodb/libbson,Machyne/libbson,derickr/libbson,ajdavis/libbson,rayyang2000/libbson,4Second2None/libbson_tmp,rcsanchez97/libbson,rayyang2000/libbson,mongodb/libbson,paulmelnikow/libbson,ajdavis/libbson,mongodb/libbson,paulmelnikow/libbson,mapr/libbson,remicollet/libbson,alexeyvo/libbson,mongodbinc-interns/libbson,mongodbinc-interns/libbson,mapr/libbson,alexeyvo/libbson,bjori/libbson,mapr/libbson,jqk6/libbson,4Second2None/libbson_tmp,derickr/libbson,derickr/libbson,4Second2None/libbson_tmp,bjori/libbson,ksuarz/libbson,paulmelnikow/libbson,4Second2None/libbson_tmp,rcsanchez97/libbson,jqk6/libbson,rayyang2000/libbson