[chore] update build scripts to create both builds using one command; details:
[chore] update build scripts to create both builds using one command; details:

- Usage is rolled back to original: `source build.sh [theme-name]`
- Now it will create 2 XML files: one for classic build and one for modern build
- The `function make_file` now accepts argument: "modern" or "classic"
- The scripts of checking file existence is moved into `function make_file`
- Variables "template_file" and "output_file" are moved into `function make_file`

Edditoria/markdown_npp