Parse lines which contain only identifiers

This is needed, so the `animation` block is correctly parsed.

src/main/grammar/StructurizrDSL.bnf

@@ -103,7 +103,7 @@
 
 structurizrDSLFile ::= statement*
 
-private statement ::= elementDefinition | scriptBlock | explicitRelationship | implicitRelationship
+private statement ::= elementDefinition | scriptBlock | explicitRelationship | implicitRelationship | identifierReferences
 
 private elementDefinition ::= singleLineStatement | blockStatement | propertyBlockStatement | CRLF
 
@@ -123,6 +123,8 @@ scriptContents ::= SCRIPT_TEXT+
 explicitRelationship ::= identifierName '->' identifierName argument*
 implicitRelationship ::= '->' identifierName argument*
 
+identifierReferences ::= identifierName+ lf_eof
+
 private keywordWithArguments ::= keyword argument*
 
 keyword ::= '!adrs' | 'animation' | 'autoLayout' | 'background' | 'border' | 'color' | 'colour' | 'component' |

src/test/kotlin/nl/dirkgroot/structurizr/dsl/parser/LineWithIdentifierReferencesTest.kt

@@ -0,0 +1,53 @@
+package nl.dirkgroot.structurizr.dsl.parser
+
+import nl.dirkgroot.structurizr.dsl.support.StructurizrDSLParserTest
+import org.junit.jupiter.api.Test
+
+class LineWithIdentifierReferencesTest : StructurizrDSLParserTest() {
+    @Test
+    fun `single identifier reference on one line`() {
+        assertPsiTree(
+            """
+                someIdentifier
+            """.trimIndent(),
+            """
+                IdentifierReferences
+                    IdentifierName someIdentifier
+            """.trimIndent()
+        )
+    }
+
+    @Test
+    fun `multiple identifier references on one line`() {
+        assertPsiTree(
+            """
+                someIdentifier1 someIdentifier2
+            """.trimIndent(),
+            """
+                IdentifierReferences
+                    IdentifierName someIdentifier1
+                    IdentifierName someIdentifier2
+            """.trimIndent()
+        )
+    }
+
+    @Test
+    fun `multiple lines with identifier references`() {
+        assertPsiTree(
+            """
+                someIdentifier1 someIdentifier2
+                someIdentifier3
+                someIdentifier4
+            """.trimIndent(),
+            """
+                IdentifierReferences
+                    IdentifierName someIdentifier1
+                    IdentifierName someIdentifier2
+                IdentifierReferences
+                    IdentifierName someIdentifier3
+                IdentifierReferences
+                    IdentifierName someIdentifier4
+            """.trimIndent()
+        )
+    }
+}