Add service newsblur

[Simx72]

Hello, this is my pull request to add the service Newsblur to the Fluentflame project.

I have added the files newsblur.ts and test_newsblur.ts.

For the implementation, I have copied other implementations from the folder services/ and adapted them to Newsblur.

For the development, I used:

• pnpm as package manager
• https://www.newsblur.com/api : The API that was implemented
• fetch and promises

There is some stuff that I still don't understand about Redux and Fluentflame Reader, like when to use dispatch and what should it return, or where are RSSSources and RSSItem stored.

However, I am pretty shure that the authenticate(), updateSources(), syncItems() and markAllRead() are implemented correctly.

I stay available for changes, concerns, etc. I'd really like to learn how it's implemented in its entirety.

[Simx72]

Oh, and I was signing with the wrong key. My bad