Set MSRV to 1.81

.github/workflows/msrv.yml

@@ -0,0 +1,24 @@
+name: Test MSRV
+
+on:
+  pull_request:
+    types: [opened, reopened, edited]
+  push:
+    branches: [ "main" ]
+    paths:
+      - ".github/workflows/msrv.yml"
+      - "demo/**"
+      - "examples/**"
+      - "src/**"
+      - "Cargo.toml"
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+    - name: Checkout
+      uses: actions/checkout@v4
+    - name: Install MSRV
+      run: rustup install 1.81
+    - name: Test on MSRV
+      run: cargo +1.81 test

Cargo.toml

@@ -1,4 +1,5 @@
 workspace = { members = ["demo"] }
+
 [package]
 name = "egui-snarl"
 version = "0.6.0"
@@ -10,6 +11,7 @@ repository = "https://github.com/zakarumych/egui-snarl"
 readme = "README.md"
 keywords = ["egui", "node", "graph", "ui", "node-graph"]
 categories = ["gui", "visualization"]
+rust-version = "1.81"
 
 [features]
 serde = ["dep:serde", "egui/serde", "slab/serde"]