migrate CI to GHA

.github/workflows/build.yml

@@ -0,0 +1,29 @@
+name: cargo-show - build & test
+on:
+  push:
+
+env:
+  CARGO_TERM_COLOR: always
+  RUST_BACKTRACE: 1
+
+jobs:
+  build_and_test:
+    name: cargo-show - latest
+    strategy:
+      fail-fast: false
+      matrix:
+        os:
+          - ubuntu-latest
+          - macos-latest
+          - windows-latest
+        toolchain:
+          - stable
+          - beta
+          - nightly
+    runs-on: ${{ matrix.os }}
+    continue-on-error: ${{ matrix.toolchain == 'nightly' }}
+    steps:
+      - uses: actions/checkout@v3
+      - run: rustup update ${{ matrix.toolchain }} && rustup default ${{ matrix.toolchain }}
+      - run: cargo build --verbose
+      - run: cargo test --verbose

update_readme.sh

@@ -12,8 +12,7 @@ cat > README.md <<EOF
 ## cargo-show
 
 [![crates.io version](https://img.shields.io/crates/v/cargo-show.svg)](https://img.shields.io/crates/v/cargo-show.svg)
-[![Build Status](https://travis-ci.org/g-k/cargo-show.svg?branch=master)](https://travis-ci.org/g-k/cargo-show)
-[![Build status](https://ci.appveyor.com/api/projects/status/m9cf5vhft7qwisas?svg=true)](https://ci.appveyor.com/project/g-k/cargo-show)
+[![Build status](https://github.com/g-k/cargo-show/actions/workflows/build.yml/badge.svg)](https://github.com/g-k/cargo-show/actions/workflows/build.yml)
 
 Prints package metadata like pip show, apt-cache show, npm view, gem query, etc.