libscratchcpp 0.8.3

Change log:

• Fixed clone scripts not stopping after the clone is deleted using "delete this clone" (#497).
• Fixed a crash when stopping a custom block using "stop this script" inside a loop (#498).
• Fixed loops getting stuck when count is a negative number (#503).
• Fixed hidden sprites starting "when this sprite clicked" scripts when clicked (#502).

Full Changelog: v0.8.2...v0.8.3