Add files for each search type. Extract config on clicking start

- Only allow adding files with appropriate file extension for each search type
  - e.g .org for org-mode search, directory for image search

- Extract file paths added to config and enablement state of each search type
  - This extracted state will be used to populate the khoj.yml config file

src/interface/desktop/file_browser.py

@@ -0,0 +1,75 @@
+# External Packages
+from PyQt6 import QtWidgets
+from PyQt6.QtCore import QDir
+
+# Internal Packages
+from src.utils.config import SearchType
+
+class FileBrowser(QtWidgets.QWidget):
+    def __init__(self, title, search_type: SearchType=None):
+        QtWidgets.QWidget.__init__(self)
+        layout = QtWidgets.QHBoxLayout()
+        self.setLayout(layout)
+        self.search_type = search_type
+
+        self.filter_name = self.getFileFilter(search_type)
+        self.dirpath = QDir.homePath()
+        self.filepaths = []
+        
+        self.label = QtWidgets.QLabel()
+        self.label.setText(title)
+        self.label.setFixedWidth(95)
+        layout.addWidget(self.label)
+        
+        self.lineEdit = QtWidgets.QLineEdit(self)
+        self.lineEdit.setFixedWidth(180)
+        
+        layout.addWidget(self.lineEdit)
+        
+        self.button = QtWidgets.QPushButton('Add')
+        self.button.clicked.connect(self.getFile)
+        layout.addWidget(self.button)
+        layout.addStretch()
+
+    def setMode(self, search_type):
+        self.search_type = search_type
+
+    def getFileFilter(self, search_type):
+        if search_type == SearchType.Org:
+            return 'Org-Mode Files (*.org)'
+        elif search_type == SearchType.Ledger:
+            return 'Beancount Files (*.bean *.beancount)'
+        elif search_type == SearchType.Markdown:
+            return 'Markdown Files (*.md *.markdown)'
+        elif search_type == SearchType.Music:
+            return 'Org-Music Files (*.org)'
+        elif search_type == SearchType.Image:
+            return 'Images (*.jp[e]g)'
+
+    def setDefaultDir(self, path):
+        self.dirpath = path
+
+    def getFile(self):
+        self.filepaths = []
+        if self.search_type == SearchType.Image:
+            self.filepaths.append(QtWidgets.QFileDialog.getExistingDirectory(self, caption='Choose Directory',
+                                                    directory=self.dirpath))
+        else:
+            self.filepaths.extend(QtWidgets.QFileDialog.getOpenFileNames(self, caption='Choose Files',
+                                                    directory=self.dirpath,
+                                                    filter=self.filter_name)[0])
+        if len(self.filepaths) == 0:
+            return
+        elif len(self.filepaths) == 1:
+            self.lineEdit.setText(self.filepaths[0])
+        else:
+            self.lineEdit.setText(",".join(self.filepaths))    
+
+    def setLabelWidth(self, width):
+        self.label.setFixedWidth(width)    
+
+    def setlineEditWidth(self, width):
+        self.lineEdit.setFixedWidth(width)
+
+    def getPaths(self):
+        return self.filepaths