Add option to format point-chapters with dots instead of hyphens

[IAMSolaara]

Feature request

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This definitely would help keeping my Komga library as automated as possible.
Every time some point-vhapters appear they tend to not get parsed as such and there can be instances like chapter 185.5 being after 210 (which disrupts the reading experience a fair bit).
This requires some manual metadata edits in Komga that would be avoidable were chapter numbers properly formatted.

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I'd like to be able to set this behavior via a command-line switch like "--dotchapters" or something like that.

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Another way to do this (but would definitely require more work) could be like youtube-dl's output format option.

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[IAMSolaara]

Since I forgot to leave it in the issue body I'll put this here.

As an example, currently Chapter 34.2 would be saved as vol_034-2.cbz.

With this implemented it should be saved as vol_034.2.cbz.

[IAMSolaara]

Hello,
after doing a little digging I found an example of where this could be done.
As most of the manga I download comes from manganato.com I started looking into its provider (and then Manganelo's).
In here I can clearly see what could be altered for this modification:

manga-py/manga_py/providers/manganelo_com.py

Lines 11 to 14 in 848a78e

	def get_chapter_index(self) -> str:
	return self.re.search(self.chapter_re, self.get_chapter())\
	.group(1).replace('.', '-')

After attempting this on a local copy though I can see a potential reason why this was done, as the left-padding of chapter numbers clearly doesn't work on floating-point values:

Nonetheless I think there can be workarounds to this (I once had this same issue (for my custom anime downloader) and I got around this by separating the number, zeropadding only the integer part and then concat-ing their string forms with a ., but I don't know how good of a workaround this is).