Improved: Add optional folder location to invokeFileDialog (Mudlet#7472)

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#### Brief overview of PR changes/additions
Allow `invokeFileDialog()` to open at an optional specified directory.
If not a valid dir or dir not specified, simply continue as per default
operation.

#### Motivation for adding to Mudlet
Allow scripters to open file dialogs at a specified place (e.g. their
scripts data location)

#### Other info (issues closed, discussion etc)

---------

Co-authored-by: Stephen Lyons <[email protected]>

src/TLuaInterpreterMudletObjects.cpp

@@ -848,15 +848,27 @@ int TLuaInterpreter::getScript(lua_State* L)
 // Documentation: https://wiki.mudlet.org/w/Manual:Lua_Functions#invokeFileDialog
 int TLuaInterpreter::invokeFileDialog(lua_State* L)
 {
+    const int n = lua_gettop(L);
+    Host& host = getHostFromLua(L);
+    QString location = mudlet::getMudletPath(mudlet::profileHomePath, host.getName());
     const bool luaDir = getVerifiedBool(L, __func__, 1, "fileOrFolder");
     const QString title = getVerifiedString(L, __func__, 2, "dialogTitle");
 
+    if (n > 2) {
+        QString target = getVerifiedString(L, __func__, 3, "dialogLocation");
+        QDir dir(target);
+
+        if (dir.exists()) {
+            location = target;
+        }
+    }
+
     if (!luaDir) {
-        const QString fileName = QFileDialog::getExistingDirectory(nullptr, title, QDir::currentPath());
+        const QString fileName = QFileDialog::getExistingDirectory(nullptr, title, location);
         lua_pushstring(L, fileName.toUtf8().constData());
         return 1;
     } else {
-        const QString fileName = QFileDialog::getOpenFileName(nullptr, title, QDir::currentPath());
+        const QString fileName = QFileDialog::getOpenFileName(nullptr, title, location);
         lua_pushstring(L, fileName.toUtf8().constData());
         return 1;
     }