Add UnitCreateEvent() on Assembler

[WilloIzCitron]

Describe the content or mechanics you are proposing.

Every Units are made from factory, reconstructor or parent unit are called UnitCreateEvent() to indicate the unit was being created, but not for Assemblers. Why?

Describe how you think this content will improve the game. If you're proposing new content, mention how it may add more gameplay options or how it will fill a new niche.

After this event was applied to Assembler, every modder can listen that event from Assemblers. and I'm as modder can implement to add Sound Indicator of recently made unit

Before making this issue, check the boxes below to confirm that you have acknowledged them.

• [X] I have checked the Trello to make sure my suggestion isn't planned or implemented in a development version.
• [X] I am familiar with all the content already in the game or have glanced at the wiki to make sure my suggestion doesn't exist in the game yet.
• [X] I have read README.md to make sure my idea is not listed under the "A few things you shouldn't suggest" category.

[github-actions[bot]]

This suggestion is now stale, and will be automatically closed.