feat(spectator): Support input signals

[kfrancois]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/ngneat/spectator/blob/master/CONTRIBUTING.md#commit
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)
• Types have been cleaned up as SpectatorDirectiveFactory, SpectatorHostFactory and their related types need some cleanup as the component's generic param is not used everywhere

PR Type

What kind of change does this PR introduce?

[ ] Bugfix
[X] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Documentation content changes
[ ] Other... Please describe:

What is the current behavior?

Issue Number: #637

What is the new behavior?

Does this PR introduce a breaking change?

[X] Yes
[ ] No

setProps and props were removed from createHostFactory and createDirectiveFactory. Props should be set through setHostProps and hostProps instead.

Other information

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[kfrancois]

This is not ready to merge, see #637

[NetanelBasal]

LGTM, let's finish it

[kfrancois]

@NetanelBasal I added some cleanup commits, are there any specific changes to docs or other changes you'd like me to make do to ensure this is in a good state to merge? I'd be glad to take them up 😄

[NetanelBasal]

We need to update the README to reflect this change:

setProps and props were removed from createHostFactory and createDirectiveFactory. Props should be set through setHostProps and hostProps instead.

[kfrancois]

Great suggestion, thanks! I added some changes to the README but if you want to make any further changes, go ahead 😄 you're much more familiar with the writing style of docs in this repo, so please make any changes you want.

(edit: I added you as collaborator to the fork so you can add any commits you want)