test: add PHPUnit test suite with JsonLdBuilder unit tests

16 unit tests covering FAQ, HowTo, Event, Recipe, LocalBusiness,
and VideoObject schema builders plus toScriptTag XSS escaping.
Closes #75

phpunit.xml.dist

@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/10.5/phpunit.xsd"
+         bootstrap="tests/bootstrap.php"
+         colors="true"
+         cacheDirectory=".phpunit.cache">
+    <testsuites>
+        <testsuite name="Unit">
+            <directory>tests/Unit</directory>
+        </testsuite>
+    </testsuites>
+    <source>
+        <include>
+            <directory>source/packages</directory>
+        </include>
+    </source>
+</phpunit>