Rewrote docs, added behaviors and more

[ffMathy]

I want to use this package in my work (I work for a corporation). However, for that to happen, I think these things that I propose here should be fixed. Alternatively I think I will make a fork at some point.

It's a big one. I hope it's okay, and that you can find the time for looking into it 🙏

Documentation

• Added new pipeline behavior example.
• Added new example of reordering execution order for both notifications and pipeline behaviors.
• Separated the documentation into "Core concepts", and then extracted the Dependency Injection part out as a separate section.

Notification handlers

• Removed the order in the decorator. This is generally bad practise, because it breaks encapsulation. If one class knows about the order of the other classes implicitly, it is typically a smell. We can't remove the need for this entirely, but we can centralize it in one place so it's easier to see what the order of handlers are (see the new documentation on changing the order). That way, it is way less likely to implicitly break, and easier to keep track of. It also follows closer with Mediatr's own setup.
• Got rid of the DispatcherInstance class. Instead, we now have mapping classes (similar, but not entirely identical). See the rest of the notes.
• The Dispatcher has a property called notifications from where the notifications mappings are controlled (and execution order).
• Added new types called INotificationClass and INotificationHandlerClass. These are used for classes instead of instances of these types. The code wrongly had INotification specified in cases where the actual real type was INotificationClass. This also strengthens the code and makes it harder to write it wrong.
• The publish method on the Mediator now returns a Promise<void> instead of Promise<void[]>.

Dispatcher

• The Dispatcher now just has two properties. notifications and behaviors, which control the handler mappings for each of them, and the order.

Pipeline behaviors

• Added support for Pipeline behaviors.
• The Dispatcher has a property called behaviors from where the pipeline behavior mappings are controlled (and execution order).
• A new decorator has been introduced for this.
• A new IPipelineBehavior interface, as well as a IPipelineBehaviorClass type has been introduced.

Boyscouting

• Changed imports to type imports where possible, to speed up compilation, and decrease the chance of accidental circular dependencies.
• Added "importsNotUsedAsValues": "error" to the tsconfig.json file, so that the TypeScript compiler will give an error if a regular import is used where a type import could have been used instead. Again, to decrease the chance of accidental circular dependencies.
• Added "strict": true to the tsconfig.json file, so that we now have full TypeScript strictness in the project.

Miscellaneous

• Bumped package version to 1.0.0.

[ffMathy]

cc @m4ss1m0g (in case you don't get notifications for this kind of stuff).

[m4ss1m0g]

@ffMathy You have done great work! Can you also update the CHANGELOG with these new improvements?

[m4ss1m0g]

Close the #5

[ffMathy]

Thanks for merging! However, I realized I forgot to follow the "keep a changelog" format, so I actually made an additional commit after. See #10 now.

Sorry about that!

[m4ss1m0g]

@ffMathy. No problem. However, you must increment 1 the patch level of packages.json, 1.0.1 otherwise I can't publish the package

[ffMathy]

I think it's actually okay to not publish the package, as only CHANGELOG.md has changed, which is not actually part of the package. Do you agree?

[m4ss1m0g]

In this case, the PR remains open, otherwise, if I merge it tries to publish and returns an error.

[m4ss1m0g]

I think is better to merge.

[ffMathy]

Awesome stuff ❤️ thanks once again.

More improvements will come, but I don't know when.

For instance, I'd like to throw an exception if the settings get mutated after they've been used once.

That way, we can tell the user if they are mutating settings after load.