Set up GH Action for R CMD check

... and the README badge.

.Rbuildignore

@@ -7,3 +7,4 @@ appveyor.yml
 ^CRAN-RELEASE$
 ^cran-comments\.md$
 ^CODE_OF_CONDUCT\.md$
+^\.github$

.github/.gitignore

@@ -0,0 +1 @@
+*.html

.github/workflows/R-CMD-check.yaml

@@ -0,0 +1,49 @@
+# Workflow derived from https://github.com/r-lib/actions/tree/v2/examples
+# Need help debugging build failures? Start at https://github.com/r-lib/actions#where-to-find-help
+on:
+  push:
+    branches: [main, master]
+  pull_request:
+    branches: [main, master]
+
+name: R-CMD-check
+
+jobs:
+  R-CMD-check:
+    runs-on: ${{ matrix.config.os }}
+
+    name: ${{ matrix.config.os }} (${{ matrix.config.r }})
+
+    strategy:
+      fail-fast: false
+      matrix:
+        config:
+          - {os: macos-latest,   r: 'release'}
+          - {os: windows-latest, r: 'release'}
+          - {os: ubuntu-latest,   r: 'devel', http-user-agent: 'release'}
+          - {os: ubuntu-latest,   r: 'release'}
+          - {os: ubuntu-latest,   r: 'oldrel-1'}
+
+    env:
+      GITHUB_PAT: ${{ secrets.GITHUB_TOKEN }}
+      R_KEEP_PKG_SOURCE: yes
+
+    steps:
+      - uses: actions/checkout@v3
+
+      - uses: r-lib/actions/setup-pandoc@v2
+
+      - uses: r-lib/actions/setup-r@v2
+        with:
+          r-version: ${{ matrix.config.r }}
+          http-user-agent: ${{ matrix.config.http-user-agent }}
+          use-public-rspm: true
+
+      - uses: r-lib/actions/setup-r-dependencies@v2
+        with:
+          extra-packages: any::rcmdcheck
+          needs: check
+
+      - uses: r-lib/actions/check-r-package@v2
+        with:
+          upload-snapshots: true

README.md

@@ -1,7 +1,6 @@
 # `networkDynamic`:  Dynamic Extensions for Network Objects
 
-[![Build Status](https://travis-ci.org/statnet/networkDynamic.svg?branch=master)](https://travis-ci.org/statnet/networkDynamic)
-[![Build Status](https://ci.appveyor.com/api/projects/status/rmj7f1xmpikh2243?svg=true)](https://ci.appveyor.com/project/statnet/networkDynamic)
+[![R build status](https://github.com/statnet/networkDynamic/workflows/R-CMD-check/badge.svg)](https://github.com/statnet/networkDynamic/actions)
 [![rstudio mirror downloads](https://cranlogs.r-pkg.org/badges/networkDynamic?color=2ED968)](https://cranlogs.r-pkg.org/)
 [![cran version](https://www.r-pkg.org/badges/version/networkDynamic)](https://cran.r-project.org/package=networkDynamic)