add CI for the GitHub mirror (!31)

as per title, this should run the same CI on the [GitHub mirror](https://github.com/dragoon-rs/dragoonfly)

.github/workflows/ci.yml

+name: Rust CI
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+  workflow_dispatch:
+
+jobs:
+  fmt:
+    runs-on: ubuntu-latest
+    if: "!contains(github.event.head_commit.message, 'draft:') && !contains(github.event.head_commit.message, 'no-ci:')"
+    steps:
+      - uses: actions/checkout@v3
+      - name: Set up Rust
+        uses: actions-rs/toolchain@v1
+        with:
+          toolchain: stable
+      - name: Run fmt check
+        run: make fmt-check
+
+  test:
+    runs-on: ubuntu-latest
+    needs: fmt
+    if: "!contains(github.event.head_commit.message, 'draft:') && !contains(github.event.head_commit.message, 'no-ci:')"
+    steps:
+      - uses: actions/checkout@v3
+      - name: Install dependencies
+        run: |
+          sudo apt update --yes
+          sudo apt upgrade --yes
+          sudo apt install protobuf-compiler --yes
+      - uses: hustcer/setup-nu@v3
+        with:
+          version: "0.95"
+      - name: Show configuration
+        run: make show
+      - name: Run tests
+        run: |
+          make check clippy
+          echo "HTTP_PROXY = ${HTTP_PROXY}"
+          echo "http_proxy = ${http_proxy}"
+          echo "HTTPS_PROXY = ${HTTPS_PROXY}"
+          echo "https_proxy = ${https_proxy}"
+          unset HTTP_PROXY
+          unset http_proxy
+          unset HTTPS_PROXY
+          unset https_proxy
+          echo "HTTP_PROXY = ${HTTP_PROXY}"
+          echo "http_proxy = ${http_proxy}"
+          echo "HTTPS_PROXY = ${HTTPS_PROXY}"
+          echo "https_proxy = ${https_proxy}"
+          export RUST_LOG=ERROR
+          make test