Adds ClickSendSMS notification provider

[tarun7singh]

Description

Adds "Click Send SMS" Notification provider
https://dashboard.clicksend.com/#/dashboard/home

Type of change

• Bug fix (non-breaking change which fixes an issue)
• User Interface
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Translation update
• This change requires a documentation update

Checklist

• My code follows the style guidelines of this project
• I ran ESLint and other linters for modified files
• I have performed a self-review of my own code and test it
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings
• My code needed automated testing. I have added them

Screenshots

[louislam]

Thanks, did you get any sms screenshot which sent from this feature?

[tarun7singh]

I have deleted messages from my phone but here's a screenshot from the clickSendDashbaord. But if you still need a message screenshot I'll resend a message.

[tarun7singh]

Here's a screenshot of message I sent again.

[Saibamen]

Please update only en.js
We will have merge conflicts with #790

[deefdragon]

I have decided to speed up and finish the rest of the notification tests tonight so they can be merged. If you could add tests for the NotificationProvider in line with #760 once thats done, that would be great.