docs/index: Group swh.* entries under a top level "API reference" entry

Closes T3737

docs/api-reference.rst

+.. _api-reference:
+
+API reference
+=============
+
+.. toctree::
+   :maxdepth: 2
+
+   swh.auth <swh-auth/index>
+   swh.core <swh-core/index>
+   swh.counters <swh-counters/index>
+   swh.dataset <swh-dataset/index>
+   swh.deposit <swh-deposit/index>
+   swh.fuse <swh-fuse/index>
+   swh.graph <swh-graph/index>
+   swh.indexer <swh-indexer/index>
+   swh.journal <swh-journal/index>
+   swh.lister <swh-lister/index>
+   swh.loader <swh-loader>
+   swh.model <swh-model/index>
+   swh.objstorage <swh-objstorage/index>
+   swh.objstorage.replayer <swh-objstorage-replayer/index>
+   swh.scanner <swh-scanner/index>
+   swh.scheduler <swh-scheduler/index>
+   swh.search <swh-search/index>
+   swh.storage <swh-storage/index>
+   swh.vault <swh-vault/index>
+   swh.web <swh-web/index>
+   swh.web.client <swh-web-client/index>

docs/index.rst

@@ -207,28 +207,8 @@ Indices and tables
    contributing/index
    tutorials/index
    faq/index
-   roadmap/roadmap-2021.rst
-   swh.auth <swh-auth/index>
-   swh.core <swh-core/index>
-   swh.counters <swh-counters/index>
-   swh.dataset <swh-dataset/index>
-   swh.deposit <swh-deposit/index>
-   swh.fuse <swh-fuse/index>
-   swh.graph <swh-graph/index>
-   swh.indexer <swh-indexer/index>
-   swh.journal <swh-journal/index>
-   swh.lister <swh-lister/index>
-   swh.loader <swh-loader>
-   swh.model <swh-model/index>
-   swh.objstorage <swh-objstorage/index>
-   swh.objstorage.replayer <swh-objstorage-replayer/index>
-   swh.scanner <swh-scanner/index>
-   swh.scheduler <swh-scheduler/index>
-   swh.search <swh-search/index>
-   swh.storage <swh-storage/index>
-   swh.vault <swh-vault/index>
-   swh.web <swh-web/index>
-   swh.web.client <swh-web-client/index>
+   roadmap/roadmap-2021
+   api-reference
    archive-changelog
    journal
    Python modules autodocumentation <apidoc/modules>