add PyYAML, toml, and SecretStorage to optional dependency list

(#3827)

README.rst

@@ -29,6 +29,9 @@ Optional
 - yt-dlp_ or youtube-dl_: Video downloads
 - PySocks_: SOCKS proxy support
 - brotli_ or brotlicffi_: Brotli compression support
+- PyYAML_: YAML configuration file support
+- toml_: TOML configuration file support for Python<3.11
+- SecretStorage_: GNOME keyring passwords for ``--cookies-from-browser``
 
 
 Installation
@@ -373,6 +376,9 @@ To authenticate with a ``mastodon`` instance, run *gallery-dl* with
 .. _PySocks:    https://pypi.org/project/PySocks/
 .. _brotli:     https://github.com/google/brotli
 .. _brotlicffi: https://github.com/python-hyper/brotlicffi
+.. _PyYAML:     https://pyyaml.org/
+.. _toml:       https://pypi.org/project/toml/
+.. _SecretStorage: https://pypi.org/project/SecretStorage/
 .. _Snapd:      https://docs.snapcraft.io/installing-snapd
 .. _OAuth:      https://en.wikipedia.org/wiki/OAuth
 .. _Chocolatey: https://chocolatey.org/install