add doc/en/scripting/filesystem.md

doc/en/scripting/filesystem.md

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+# Filesystem and serialization
+
+### *file* library
+
+Filesystem interaction library.
+
+```python
+file.resolve(path: str) -> str
+```
+
+Function turns `entry_point:path` (example `user:worlds/house1`) to a regular path. (example `C://Users/user/.voxeng/worlds/house1`)
+
+> [!NOTE]
+> The function should be used for debug only. *entry_point:path* notation is required in all **file** functions.
+
+Resulting path is not canonical and may be relative.
+
+```python
+file.read(path: str) -> str
+```
+
+Read whole text file.
+
+```python
+file.read_bytes(path: str) -> array of integers
+```
+
+Read file into bytes array.
+
+```python
+file.write(path: str, text: str) -> nil
+```
+
+Overwrite text file.
+
+```python
+file.write_bytes(path: str, data: array of integers)
+```
+
+Overwrite binary file with bytes array.
+
+```python
+file.length(path: str) -> int
+```
+
+Get file length (bytes) or 0.
+
+```python
+file.exists(path: str) -> bool
+```
+
+Check if file or directory exist.
+
+```python
+file.isfile(path: str) -> bool
+```
+
+Check if the path points to a file.
+
+```python
+file.isdir(path: str) -> bool
+```
+
+Check if the path points to a directory.
+
+```python
+file.mkdir(path: str) -> bool
+```
+
+Create directory. Returns true if new directory created
+
+```python
+file.mkdirs(path: str) -> bool
+```
+
+Create directories chain. Returns true if new directory created.
+
+## Storing data in a world
+
+When saving pack data in the world, you should use the function:
+
+```python
+pack.data_file(packid: str, filename: str) -> str
+```
+
+Returns data file path like: `world:data/packid/filename`
+and creates missing directories.
+
+If paths other than `data/{packid}/...` are used, data may be lost.