feat: add custom separator to filenamePattern

[mengshouer]

I don't know Japanese, so I use translation software for Japanese i18n.

[EltonChou]

Thanks for your PR.

Several problems need to be solved,

1. Can all characters be in a valid filename or path in most OS ?
2. Can this feature be easily adopted by most of the users without any unexpected error ?
3. If error happens, how do they get the feedback ?
4. Providing a well-tested seperator list rather than an input ?
5. Is the generated filename easily parsed ?

[mengshouer]

I hadn't thought about it much, and there are some special characters that different operating systems don't allow. You can set the option to turn it off by default and consider adding a warning flag if you want to use it or turn off the PR.

Since I'm changing it for my own use, I can just use the locally built version.