Net 4.5 support is now problematic

[flytzen]

I have just set up a new computer and it is no longer possible to add a developer pack for .Net 4.5; only 4.5.1 and 4.5.2 are available.
I can still compile from the commandline, but VS 2022 won't compile the solution.
If we change support to 4.5.2, we'll have to increment the major version number. But, when #69 is resolved, we will almost certainly need to drop support for 4.5.x anyway - so probably better to wait and see what the next version of QR Coder supports, align ourselves with that and release a major version then?

[ahwm]

We'll need to add net60 support then as well, so that makes sense.

[ahwm]

@flytzen @BrandonPotter additional idea for a 3.0 - what if we completely decouple from a QR generator and leave it up to the developer to choose a library? Thoughts?

[flytzen]

@flytzen @BrandonPotter additional idea for a 3.0 - what if we completely decouple from a QR generator and leave it up to the developer to choose a library? Thoughts?

I see where you are coming from....
But, I think it makes it more difficult to pick up for a consumer and I don't see it adding any value for them? I like that it "just works" right now and judging by some of the support questions we've had, I think some of the consumers would quickly give up if we asked them to do this themselves.

If we want to speed up .Net 6.0, we can just change the library we use. We can even multi-target it so we use different libraries on different framework versions, if needed. In that case, we just need to make sure the "size" parameter produces consistently sized images across frameworks.

[flytzen]

Related to #107