added Viber Bot API support (based on Twillo SMS plugin )

[Delphi251189]

To release a new version of a plugin, we suggest the following checklist. Checking these locally before pushing to the repository gives you immediate feedback, instead of waiting for the repository to automatically run the checks.

• update the information.version in manifest.json; please use semantic versioning ("major.minor.patch", e.g. "1.4.2" - major can break compatibility, minor can introduce compatible new features, patch is for bug fixes)
• in the project root directory, run bash php-cs-check.sh to check for valid PHP code
  • normally, this should report no errors
  • if any found, please fix - these could prevent your plugin from working
• in the plugins/ directory, run php ../pack-plugin.php $YOUR_PLUGIN, where $YOUR_PLUGIN is the directory name of your plugin; this creates the installable package
  • if you have a composer.json, this will check it and install the dependencies - if this reports as "outdated", please fix by running composer update in your plugin's directory
  • normally, this should finish without errors or warnings
• in the project root directory, run php validate.php
  • normally, this should report 0 errors
  • if it complains that plugins.json is outdated, run php generate-json.php > plugins.json to update it.
• commit the changes made during these steps