add feature to export all defined micros to file one time for backup

[rfhamz]

Describe the feature and the current behavior/state

add feature to export all defined micros to file one time for backup, currently, I have to export the macros one by one

Who will benefit with this feature?

the user

Any Other info

[sunderme]

you can find the macros in .config/texstudio/macro

[octaeder]

Note: If implemented, user manual needs update of statement "macros can be im- and exported to a file (one by one)."