feat(hydrogen): add ansible role for deployment using docker

roles/hydrogen/README.md

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+# `finallycoffee.matrix.hydrogen` ansible role
+
+Deploy [hydrogen](https://matrix.org/ecosystem/clients/hydrogen/),
+a lightweight matrix web client with SSO, multi-account and E2EE
+Support.
+
+## Configuration
+
+All configuration keys which would be written in the `config.json`
+are available under the `hydrogen_config_*` as flattened camelcase keys.
+As an alternative, the entire config structure can be passed into
+`hydrogen_config` (in combine mode) or `hydrogen_full_config` (ignores
+all defaults).