[Enhancement] Custom media lifecycle scripts (#219)

* Namespaced notification modules under lifecycle

* Added a JSON encoder for all the main model types

* Added startup task to create user script file

* Hook up user script event to media download

* Hooked up media deletion user script

* Added jq to docker deps

* Updated README

selfhosted.Dockerfile

@@ -79,7 +79,7 @@ ARG PORT=8945
 
 RUN apt-get update -y
 RUN apt-get install -y libstdc++6 openssl libncurses5 locales ca-certificates \
-  ffmpeg curl git openssh-client nano python3 python3-pip
+  ffmpeg curl git openssh-client nano python3 python3-pip jq procps
 RUN apt-get clean && rm -f /var/lib/apt/lists/*_*
 
 # Download and update YT-DLP