Minor Folding improvements

[ssratkevich]

You beat me to it by literally a few hours.
So I looked at the resulting code and suggest a few small improvements to get it a bit more readable.
It's a pitty that we couldn't use ReadOnlySpan<>, but for now it's fine.
Also I noticed wrong array length 76 instead of 75.
You see it in a moment in my PR, that follows.

[axunonb]

You see our activities for a couple of improvements in ical.net. Is there a chance you gave us a helping hand?

[axunonb]

Now you found the best iCalendar library for .Net 👍
We'd like to publish a first v5 preview version on NuGet, but some kind of migration guide would help people to move away from v4.
Is this something you could contribute?
Or #274?

[ssratkevich]

Now you found the best iCalendar library for .Net 👍

It seems so.

Is there a chance you gave us a helping hand?

I could try.

You see our activities for a couple of improvements in ical.net.

As I notice, it's another place for improvement:
IStringSerializer.SerializeToString implementations in all classes.
My suggestion to use common (single) StringBuilder all the way for calendar building (drilling it upside down).

What do you say about it?

Or #274?

I need more time to explore all of the library to figure out its interconnections and probably to finish with reading RFC-5545 to be more precise.

[axunonb]

@minichma and I are working on ical.net since October, so we're well aware of a certain learning curve.
Diving into it is the best teacher though.