feat: add LocalDateConverter and LocalDateTimeConverter

src/main/java/io/github/r4tylmz/betterpoi/converters/LocalDateConverter.java

@@ -0,0 +1,22 @@
+package io.github.r4tylmz.betterpoi.converters;
+
+import org.apache.commons.beanutils.Converter;
+
+import java.time.LocalDate;
+
+public class LocalDateConverter implements Converter {
+    @Override
+    public <T> T convert(Class<T> type, Object value) {
+        if (value == null) {
+            return null;
+        }
+
+        if (value instanceof LocalDate) {
+            return (T) value;
+        }
+        if (value instanceof java.util.Date) {
+            return (T) ((java.util.Date) value).toInstant().atZone(java.time.ZoneId.systemDefault()).toLocalDate();
+        }
+        return null;
+    }
+}

src/main/java/io/github/r4tylmz/betterpoi/converters/LocalDateTimeConverter.java

@@ -0,0 +1,23 @@
+package io.github.r4tylmz.betterpoi.converters;
+
+import org.apache.commons.beanutils.Converter;
+
+import java.time.LocalDateTime;
+
+public class LocalDateTimeConverter implements Converter {
+    @Override
+    public <T> T convert(Class<T> type, Object value) {
+        if (value == null) {
+            return null;
+        }
+
+        if (value instanceof LocalDateTime) {
+            return (T) value;
+        }
+
+        if (value instanceof java.util.Date) {
+            return (T) ((java.util.Date) value).toInstant().atZone(java.time.ZoneId.systemDefault()).toLocalDateTime();
+        }
+        return null;
+    }
+}