replace travis with Github Actions (bitcoin#1432)

replace travis with Github Actions

.github/workflows/github-action-checks.yml

@@ -0,0 +1,19 @@
+name: GitHub Actions Check
+run-name: ${{ github.actor }} Checks 🚀
+on: [push, pull_request]
+jobs:
+  Link-Format-Checks:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - run: scripts/link-format-chk.sh
+  Build-Table-Checks:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - run: scripts/buildtable.pl >/tmp/table.mediawiki || exit 1
+  Diff-Checks:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - run: scripts/diffcheck.sh

scripts/diffcheck.sh

@@ -0,0 +1,13 @@
+#!/bin/bash
+
+diff README.mediawiki /tmp/table.mediawiki | grep '^[<>] |' >/tmp/after.diff || true
+if git checkout HEAD^ && scripts/buildtable.pl >/tmp/table.mediawiki 2>/dev/null; then
+    diff README.mediawiki /tmp/table.mediawiki | grep '^[<>] |' >/tmp/before.diff || true
+    newdiff=$(diff -s /tmp/before.diff /tmp/after.diff -u | grep '^+')
+    if [ -n "$newdiff" ]; then
+        echo "$newdiff"
+        exit 1
+    fi
+else
+    echo 'Cannot build previous commit table for comparison'
+fi