Sqlean.py

Changes in the [fileio](https://github.com/nalgeon/sqlean/blob/main/docs/fileio.md) extension:

- `fileio_append(path, str)` appends a string to a file.
- `fileio_read(path, offset, limit)` reads a file fragment.

Thanks to phrrngtn for `fileio_read` improvements! (68)

Consistent function naming for the [fileio](https://github.com/nalgeon/sqlean/blob/main/docs/fileio.md) extension:


readfile -> fileio_read
scanfile -> fileio_scan
writefile -> fileio_write
mkdir -> fileio_mkdir
symlink -> fileio_symlink
lsdir -> fileio_ls
lsmode -> fileio_mode


Old names still work for the sake of backward compatibility.

Added the `scanfile` function to the [fileio](https://github.com/nalgeon/sqlean/blob/main/docs/fileio.md) extension:

scanfile(path)

Reads the file specified by `path` line by line, without loading the whole file into memory.


sqlite> select rowid, value, name from scanfile('hello.txt');
┌───────┬───────┬───────────┐
│ rowid │ value │ name │
├───────┼───────┼───────────┤
│ 1 │ one │ hello.txt │
│ 2 │ two │ hello.txt │
│ 3 │ three │ hello.txt │
└───────┴───────┴───────────┘

Optimized [regexp](https://github.com/nalgeon/sqlean/blob/main/docs/regexp.md) performance.

Unicode support in the [regexp](https://github.com/nalgeon/sqlean/blob/main/docs/regexp.md) extension.

This release brings the [regexp](https://github.com/nalgeon/sqlean/blob/main/docs/regexp.md) extension for all operating systems. It supports all major regular expression features. The old `re` extension is deprecated.