Add a CI job to make sure relaychain produces blocks (#16)

.github/actions/free-disk-space/action.yml

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+name: Free disk space
+description: We've run into out-of-disk error when compiling Rust projects, so we free up some space this way.
+
+runs:
+  using: "composite"
+  steps:
+    - name: Free Disk Space
+      uses: jlumbroso/free-disk-space@54081f138730dfa15788a46383842cd2f914a1be # 1.3.1
+      with:
+        android: true # This alone is a 12 GB save.
+        # We disable the rest because it caused some problems. (they're enabled by default)
+        # The Android removal is enough.
+        dotnet: false
+        haskell: false
+        large-packages: false
+        swap-storage: false

.github/actions/macos-dependencies/action.yml

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+name: Install macOS dependencies
+description: Installs dependencies required to compile the template on macOS
+
+runs:
+  using: "composite"
+  steps:
+    - run: |
+        curl https://sh.rustup.rs -sSf -y | sh
+        brew install protobuf
+        rustup target add wasm32-unknown-unknown --toolchain stable-aarch64-apple-darwin
+        rustup component add rust-src --toolchain stable-aarch64-apple-darwin
+      shell: sh

.github/actions/ubuntu-dependencies/action.yml

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+name: Install Ubuntu dependencies
+description: Installs dependencies required to compile the template in Ubuntu
+
+runs:
+  using: "composite"
+  steps:
+    - name: Rust compilation prerequisites (Ubuntu)
+      if: contains(matrix.os, 'ubuntu')
+      run: |
+        sudo apt update
+        sudo apt install -y \
+          protobuf-compiler
+        rustup target add wasm32-unknown-unknown
+        rustup component add rustfmt clippy rust-src
+      shell: bash