fix encoding error while reading from UTF-8 file + add .gitignore + run linter

[vdmitriyev]

List of changes

• Fix encoding error while reading from UTF-8 file
• Add .gitignore
• Run black linter over the code - https://github.com/psf/black

[vdmitriyev]

It looks like a lot of changes have been introduced. But it is basically log .gitignore and black linter modifications.
The only part that has been changed is:

import traceback

def next_file(file: str) -> None:

    global tex, tex_lines, tex_lines_clean, in_env, envs
    try:
        with open(file, mode="r", encoding="utf-8") as content_file:
            tex = content_file.read()
    except:
        print("Could not open '%s'" % sys.argv[1])
        print(f"Error: {traceback.format_exc()}")
        sys.exit(1)