Document how and when to use go-task solbuild-reset in the appropriate place in the docs

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Single-sourcing a guaranteed-working workflow for users to reset their solbuild images and cache, can be useful in terms of eliminating all variables related to solbuild state and spurious build issues.

To ensure that this would be as quick a process as possible, I did some research here that resulted in me speeding up solbuild image decompression here, which in turn has resulted in the entire go-task solbuild-reset run now taking about the same time as a single solbuild update -i operation did for me previously.