Add Sonarr Cloudron app package

- Add CloudronManifest.json with app configuration
- Add Dockerfile for building Sonarr v4 image
- Add start.sh script to launch Sonarr
- Add icon.png for app icon
- Update README.md with installation and usage instructions

Dockerfile

@@ -0,0 +1,20 @@
+FROM --platform=amd64 cloudron/base:4.2.0@sha256:46da2fffb36353ef714f97ae8e962bd2c212ca091108d768ba473078319a47f4
+
+RUN apt-get update -y && \
+    apt-get install -y curl sqlite3 dpkg wget && \
+    apt-get clean && \
+    rm -rf /var/lib/apt/lists/*
+
+RUN mkdir -p /app/code/sonarr
+WORKDIR /app/code
+
+RUN wget --content-disposition "https://services.sonarr.tv/v1/download/master/latest?version=4&os=linux&arch=x64" -O Sonarr.tar.gz && \
+    tar -xvzf Sonarr.tar.gz -C /app/code/sonarr && \
+    rm Sonarr.tar.gz
+
+COPY start.sh /app/code/
+RUN chmod +x /app/code/start.sh && \
+    chown -R cloudron:cloudron /app/code/sonarr
+
+CMD [ "/app/code/start.sh" ]
+