Fix bitflags breaking MSRV

Author: kvark

.github/workflows/ci.yaml

@@ -21,6 +21,18 @@ jobs:
           toolchain: ${{ matrix.rust }}
           profile: minimal
           override: true
+      - uses: actions-rs/cargo@v1
+        name: Downgrade bitflags to MSRV
+        if: ${{ matrix.rust }} == "1.36.0"
+        with:
+          command: update
+          args: -p bitflags --precise 1.2.1
+      - uses: actions-rs/cargo@v1
+        name: Downgrade indexmap to MSRV
+        if: ${{ matrix.rust }} == "1.36.0"
+        with:
+          command: update
+          args: -p indexmap --precise 1.6.2
       - run: cargo test
       - run: cargo test --all-features