fixed entry placeholder for textvariables and added test_entry_placeholder.py

test/manual_integration_tests/text_entry_placeholder.py

@@ -0,0 +1,27 @@
+import customtkinter
+
+app = customtkinter.CTk()  # create CTk window like you do with the Tk window (you can also use normal tkinter.Tk window)
+app.geometry("400x400")
+app.title("test_entry_placeholder.py")
+
+str_var = customtkinter.StringVar(value="test")
+
+entry_1 = customtkinter.CTkEntry(app, placeholder_text="placeholder", textvariable=str_var)
+entry_1.pack(pady=20)
+
+entry_2 = customtkinter.CTkEntry(app, placeholder_text="placeholder", textvariable=str_var)
+entry_2.pack(pady=20)
+entry_2.insert(0, "sdfjk ")
+entry_2.delete(0, 2)
+
+entry_3 = customtkinter.CTkEntry(app, placeholder_text="placeholder")
+entry_3.pack(pady=(40, 20))
+entry_3.insert(0, "sdfjk")
+entry_3.delete(0, "end")
+
+entry_4 = customtkinter.CTkEntry(app, placeholder_text="password", show="*")
+entry_4.pack(pady=(20, 20))
+entry_4.insert(0, "sdfjk")
+entry_4.delete(0, 2)
+
+app.mainloop()