Add minSize option

[larionov]

Adds minSize, --min-size option to fail if size of the bundle is too small.

Description

Motivation and Context

Fixes #207. Sometimes it's useful to also have a warning when your bundle suddenly becomes too small, maybe that wasn't intentional. This crosses a bit into the functional tests realm but this check I think is simple enough and could serve as a sanity check for some hard-to-test changes, like in css bundles, which require visual/screenshot testing that is not always done.

Even if functional tests for your build are implemented I think the name bundlesize and maxSize options do imply that this tool made for the checking all the things about allowed sizes of files, so it makes sense to keep the information about minimal allowed sizes in the same config.

Screenshots (if appropriate):

Types of changes

• New feature (non-breaking change which adds functionality)

[safonoi]

It's very use useful for controlling the minimum chunk size. Please review PR. We are waiting for this feature.

[SmolinPavel]

This is the feature we are waiting for!