Support trailing comments (#38)

The original Ruby dotenv supports trailing comments as it is valid shell
syntax. In general it would be good to conform to the regular expression
as defined here:
https://github.com/bkeepers/dotenv/blob/master/lib/dotenv/parser.rb#L14-L30

Co-authored-by: Carmine DiMascio <cdimasci@amazon.com>

src/main/java/io/github/cdimascio/dotenv/internal/DotenvParser.java

@@ -19,7 +19,7 @@
 public class DotenvParser {
 
     private static final Pattern WHITE_SPACE_REGEX = Pattern.compile("^\\s*$"); // ^\s*${'$'}
-    private static final Pattern DOTENV_ENTRY_REGEX = Pattern.compile("^\\s*([\\w.\\-]+)\\s*(=)\\s*(.*)?\\s*$"); // ^\s*([\w.\-]+)\s*(=)\s*(.*)?\s*$
+    private static final Pattern DOTENV_ENTRY_REGEX = Pattern.compile("^\\s*([\\w.\\-]+)\\s*(=)\\s*([^#]*)?\\s*(#.*)?$"); // ^\s*([\w.\-]+)\s*(=)\s*([^#]*)?\s*(#.*)?$
 
     private final DotenvReader reader;
     private final boolean throwIfMissing;

src/test/java/tests/BasicTests.java

@@ -15,6 +15,7 @@ public class BasicTests {
         put("MY_TEST_EV2", "my test ev 2");
         put("WITHOUT_VALUE", "");
         put("MULTI_LINE", "hello\\nworld");
+        put("TRAILING_COMMENT", "value");
     }};
 
     @Test(expected = DotenvException.class)

src/test/resources/.env

@@ -3,6 +3,7 @@ MY_TEST_EV1=my test ev 1
 MY_TEST_EV2=my test ev 2
 WITHOUT_VALUE=
 MULTI_LINE=hello\nworld
+TRAILING_COMMENT=value # comment
 
 ## Malformed EV!
 MY_TEST_EV3

src/test/resources/env

@@ -3,6 +3,7 @@ MY_TEST_EV1=my test ev 1
 MY_TEST_EV2=my test ev 2
 WITHOUT_VALUE=
 MULTI_LINE=hello\nworld
+TRAILING_COMMENT=value # comment
 
 ## Malformed EV!
 MY_TEST_EV3