fix(docs): add iterative-bootstrap proposal to toctree

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Signed-off-by: Rohan Devasthale <rdevasth@redhat.com>

Author: rd4398

docs/proposals/index.rst

@@ -4,6 +4,7 @@ Fromager Enhancement Proposals
 .. toctree::
    :maxdepth: 1
 
+   iterative-bootstrap
    new-patcher-config
    new-resolver-config
    release-cooldown