feat: add initial project setup with IntelliJ configuration, message …

…localization, and MessageSourceService

- Added IntelliJ IDEA project files for configuration and code styles.
- Introduced MessageSourceService class for handling internationalization (i18n).
- Included English and Turkish localization files for validation and error messages.
- Added `.gitignore` with Java, Maven, Gradle, IntelliJ, and other standard entries.
- Configured Maven settings for accessing GitHub repositories.

.github/settings.xml

@@ -0,0 +1,7 @@
+<servers>
+    <server>
+        <id>github</id>
+        <username>YOUR_GITHUB_USERNAME</username>
+        <password>YOUR_GITHUB_TOKEN</password>
+    </server>
+</servers>

src/main/java/io/github/r4tylmz/betterpoi/i18n/MessageSourceService.java

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+package io.github.r4tylmz.betterpoi.i18n;
+
+import java.text.MessageFormat;
+import java.util.Locale;
+import java.util.ResourceBundle;
+
+/**
+ * Service for handling internationalization (i18n) of messages.
+ * This class is compatible with Java 1.8 and uses standard Java libraries.
+ */
+public class MessageSourceService {
+    private static final String BUNDLE_NAME = "messages";
+    private final ResourceBundle bundle;
+
+    /**
+     * Creates a new MessageSourceService for the specified locale.
+     *
+     * @param locale the locale to use for messages
+     */
+    public MessageSourceService(Locale locale) {
+        this.bundle = ResourceBundle.getBundle(BUNDLE_NAME, locale);
+    }
+
+    /**
+     * Creates a MessageSourceService using the system default locale.
+     *
+     * @return a new MessageSourceService instance
+     */
+    public static MessageSourceService createDefault() {
+        return new MessageSourceService(Locale.getDefault());
+    }
+
+    /**
+     * Creates a MessageSourceService for the specified language.
+     *
+     * @param language the language code (e.g., "en" for English, "tr" for Turkish)
+     * @return a new MessageSourceService instance
+     */
+    public static MessageSourceService forLocale(String language) {
+        return new MessageSourceService(new Locale(language));
+    }
+
+    /**
+     * Gets a localized message with the given key and formats it with the provided arguments.
+     *
+     * @param key  the message key in the resource bundle
+     * @param args the arguments to format the message with
+     * @return the formatted localized message
+     */
+    public String getMessage(String key, Object... args) {
+        String pattern = bundle.getString(key);
+        return MessageFormat.format(pattern, args);
+    }
+}

src/main/resources/messages.properties

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+pattern.validation.error=Cell value [{0}] is not valid. Cell value must match with the pattern: {1}
+required.validation.error=Header [{0}] is required and cannot be null or empty.
+duplicate.row.error=Duplicate row found
+header.mismatch.error=Column header mismatch at index {0}. Expected: {1}, Found: {2}
+workbook.null.error=workbook can't be null
+workbook.class.null.error=WorkBookClass must not be null
+sheet.not.found.error=Unable to find sheet with name: {0}

src/main/resources/messages_tr.properties

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+pattern.validation.error=Hücre değeri [{0}] geçerli değil. Hücre değeri şununla eşleşmeli: {1}
+required.validation.error=Başlık [{0}] zorunludur ve boş bırakılamaz.
+duplicate.row.error=Yinelenen satır bulundu
+header.mismatch.error={0} indeksinde sütun başlığı uyuşmazlığı var. Beklenen: {1}, Bulunan: {2}
+workbook.null.error=Çalışma kitabı boş olamaz
+workbook.class.null.error=Çalışma kitabı sınıfı boş olamaz
+sheet.not.found.error=Belirtilen isimde sayfa bulunamadı: {0}