Feature: Add option for additional files/folders to be watched

[urrri]

Is your feature request related to a problem? Please describe.

Some files, used as mock dependencies can be out of the mock folder(s). E.g. configurations, files shared with main project, etc.
To make sure any related change in that files accepted by mocker, they also should be watched.

Describe the solution you'd like

MockerOption can have a field like filesToWatch (additionalFilesToWatch, watchFiles, etc., next to the field watchOptions), that can contain array of additional files and folders.
All that entries should be added to watch list, but not to mock list.
The minimal resolution should be file, because it can be, for example, placed at the root folder of a project and we don't want to watch the whole project.

Issue Checklist

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