Add workaround to solve headless test failure on Windows OS

For headless test task, 'prism.order' property is used to choose the
graph renderer to use. Currently, we specify this property to be 'sw'.

However, this property triggers a bug of openjdk-jfx with headless
mode [1]. This property will cause Java Runtime Error for Windows OS
including AppVeyor:

    # A fatal error has been detected by the Java Runtime Environment:
    #
    #  EXCEPTION_ACCESS_VIOLATION (0xc0000005) at pc=0x00007ffd95b64879, pid=1476, tid=2640
    #
    # JRE version: OpenJDK Runtime Environment (11.0.1+13) (build 11.0.1+13)
    # Java VM: OpenJDK 64-Bit Server VM (11.0.1+13, mixed mode, tiered, compressed oops, g1 gc, windows-amd64)
    # Problematic frame:
    # C  [javafx_font.dll+0x4879]

This bug has been identified and will be fixed in future release [2].
Let's use the workaround suggested [3] to solve the problem.

[1] javafxports/openjdk-jfx#66
[2] javafxports/openjdk-jfx#66 (comment)
[3] javafxports/openjdk-jfx#66 (comment)

build.gradle

@@ -65,6 +65,7 @@ dependencies {
     implementation group: 'org.openjfx', name: 'javafx-web', version: javafxVersion, classifier: 'mac'
     implementation group: 'org.openjfx', name: 'javafx-web', version: javafxVersion, classifier: 'linux'
 
+    implementation group: 'org.apache.commons', name: 'commons-lang3', version: '3.8.1'
     implementation group: 'com.fasterxml.jackson.core', name: 'jackson-databind', version: '2.7.0'
     implementation group: 'com.fasterxml.jackson.datatype', name: 'jackson-datatype-jsr310', version: '2.7.4'
 

src/test/java/seedu/address/ui/GuiUnitTest.java

@@ -2,6 +2,7 @@
 
 import java.util.Optional;
 
+import org.apache.commons.lang3.SystemUtils;
 import org.junit.Rule;
 
 import guitests.GuiRobot;
@@ -18,6 +19,12 @@ public abstract class GuiUnitTest {
 
     protected final GuiRobot guiRobot = new GuiRobot();
 
+    static {
+        if (SystemUtils.IS_OS_WINDOWS) {
+            System.load("C:\\Windows\\System32\\WindowsCodecs.dll");
+        }
+    }
+
     /**
      * Retrieves the {@code query} node owned by the {@code rootNode}.
      *