Feat: Add nvim-notify support

[agoodshort]

As the title says, this adds support for nvim-notify.

The idea so far is to check if nvim-notify is installed, and if it is, we use vim.notify() to display the loading status.

I'm not sure how most people use nvim-notify and if they hook vim.notify = require("notify") as described in the README.
I personally use it through noice and this implementation works as expected. Maybe someone from #131 can shime in.

Next steps/questions:

• Update docs?
• Should it be configurable?

recording_20231005-234247.webm

(Kinda cool I received an error message during my recording 🥲)

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Credit to this snippet which helped a lot to understand how to replace an existing notification

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Closes #131

[vuki656]

Looks good. Thanks for implementing it.

As for the configurability, maybe see it people want it and add it then, not sure. Up to you :D

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As for the error, I saw it happens and not sure why. I don't use the plugin myself that much so I haven't prioritized fixing it. If you are up for it, I'd be glad to help.

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As for the docs, maybe add a note somewhere that notify is supported and put this video. I think that would work. Maybe without the error :D

[agoodshort]

I am gone on holidays, will be back on a PC towards the end of October. I will then work on the points above.
Hope we get some feedback from people by then.