Replace fill-available to stretch

[bonchuk]

When running "npm start", a warning message appears stating that
"(1:757) autoprefixer: Replace fill-available with stretch, as the specification has been changed."
To address this issue, can you modify the file located at "@ ./node_modules/react-pure-modal/dist/react-pure-modal.min.css"?

[vlad-ciorba]

@sanya-shch fixed this warning back in 2020 (#48), but unfortunately it was never merged.

[max-mykhailenko]

@vlad-ciorba feel free to retest that PR and I'll merge it

[vlad-ciorba]

@max-mykhailenko It got old and has merge conflicts, but I retested it and opened a new PR.
Please see #87