Refine formatter comp regex

Update the regex to completely remove the formatter comment line.

Closes gh-21

Author: philwebb

src/main/java/io/spring/asciidoctor/backend/codetools/ChompListingContentConverter.java

@@ -167,7 +167,7 @@ private String chompFilePatterns(String content) {
 
 	private static class FormatterChomper implements Chomper {
 
-		private static final Pattern PATTERN = Pattern.compile("^\\s*\\/\\/\\s*@formatter:(on|off).*\n?$",
+		private static final Pattern PATTERN = Pattern.compile("^[\\ \\t]*\\/\\/\\s*@formatter:(on|off).*$\n?",
 				Pattern.MULTILINE);
 
 		@Override

src/test/java/io/spring/asciidoctor/backend/codetools/ChompListingContentConverterTests.java

@@ -87,6 +87,11 @@ void convertWhenFormattersChompReturnsChompedLines(ConvertedHtml html) {
 		assertThat(html.getElementHtml("code")).isEqualTo("public class Example {}");
 	}
 
+	@Test
+	void convertWhenMethodFormattersChompReturnsChompedLines(ConvertedHtml html, ExpectedHtml expected) {
+		assertThat(html.getElementHtml("code")).satisfies(expected);
+	}
+
 	@Test
 	void convertWhenMultipleChompsReturnsChompedLines(ConvertedHtml html, ExpectedHtml expected) {
 		assertThat(html.getElementHtml("code")).satisfies(expected);

src/test/resources/io/spring/asciidoctor/backend/codetools/ChompListingContentConverterTests_convertWhenMethodFormattersChompReturnsChompedLines.adoc

@@ -0,0 +1,15 @@
+= Test Document
+:chomp: formatters
+
+[source,java]
+----
+public class Example {
+
+	public void method() {
+		// @formatter:off
+		new StringBuilder();
+		// @formatter:on
+	}
+
+}
+----

src/test/resources/io/spring/asciidoctor/backend/codetools/ChompListingContentConverterTests_convertWhenMethodFormattersChompReturnsChompedLines_expected.html

@@ -0,0 +1,7 @@
+public class Example {
+
+	public void method() {
+		new StringBuilder();
+	}
+
+}