feat(database): add Excel toolchain functions

Added new ExcelToolchainFunction class in the database module. This class includes functions for handling Excel files, such as checking applicability, executing functions, and converting between markdown and Excel formats.

toolsets/database/src/main/kotlin/com/phodal/shire/database/excel/ExcelToolchainFunction.kt

@@ -0,0 +1,37 @@
+package com.phodal.shire.database.excel
+
+import com.intellij.openapi.project.Project
+import com.intellij.psi.PsiBinaryFile
+import com.intellij.psi.PsiManager
+import com.phodal.shirecore.provider.function.ToolchainFunctionProvider
+
+class ExcelToolchainFunction : ToolchainFunctionProvider {
+    override fun isApplicable(project: Project, funcName: String): Boolean {
+        return funcName == "excel"
+    }
+
+    override fun execute(project: Project, funcName: String, args: List<Any>, allVariables: Map<String, Any?>): Any {
+        return "excel"
+    }
+
+    /// markdown to excel
+    fun markdownToExcel(project: Project, content: String): String {
+        return "excel"
+    }
+
+    /// excel to markdown
+    fun excelToMarkdown(project: Project, filePath: String): String? {
+        val file = project.baseDir.findFileByRelativePath(filePath)
+            ?: throw IllegalArgumentException("File not found: $filePath")
+        val excelFile = PsiManager.getInstance(project).findFile(file)
+
+        if (excelFile !is PsiBinaryFile) {
+            throw IllegalArgumentException("File is not a binary file: $filePath")
+        }
+
+//        val config = BaseExtractorConfig()
+//        val xlsxValuesExtractor = XlsxExtractorFactory().createExtractor(config)
+//        xlsxValuesExtractor.startExtraction()
+        return excelFile?.text
+    }
+}