How do I open a text file using myst-nb?

[fcarvalhopacheco]

Hi, I am trying to open a .txt file without success. I keep getting `FileNotFoundError: [Errno 2] No such file or directory:

Please see the code below.

---
jupytext:
  text_representation:
    extension: .md
    format_name: myst
kernelspec:
  display_name: Python 3
  language: python
  name: python3

---

```{code-cell} python3 
:file: docs/source/_static/employee_data.txt

class Employee:
    MIN_SALARY = 30000
    def __init__(self, name, salary=30000):
        self.name = name
        if salary >= Employee.MIN_SALARY:
            self.salary = salary
        else:
            self.salary = Employee.MIN_SALARY
    @classmethod
    def from_file(cls,filename):
        with open(filename,"r") as f:
            name = f.readline()
        return cls(name)


emp1 = Employee.from_file("docs/source/_static/employee_data.txt")
print(type(emp1))
print(emp1.name, str(emp1.salary))

emp2 = Employee("fernando", 500000)
print(type(emp2))
print(emp2.name, str(emp2.salary))

```

i have already tried different combinations but also without success

:file: _static/employee_data.txt
emp1 = Employee.from_file("_static/employee_data.txt")

:file: _static/employee_data.txt
emp1 = Employee.from_file("employee_data.txt")

:file: source/_static/employee_data.txt
emp1 = Employee.from_file("source/_static/employee_data.txt")

I also tried load

:load: “source/_static/employee_data.tx”
:load: “source/_static/“

Maybe also related to #262