clear cache offline button

[harshithpabbati]

Fixes #793

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[harshithpabbati]

FInally done 👍

[harshithpabbati]

FInally done

Sorry because I deleted that branch So I created a new one.

[harshithpabbati]

@publiclab/is-reviewers

[harshithpabbati]

@jywarren review this.