Reduce slug size by more than 2 times

[kenteltest]

1. Reduce the size of the image by 30mb by preventing downloading and copying unnecessary .net runtime
2. Reduce the size of the image by 2 times by removing unnecessary building artifacts (bin and obj dirs)

[jincod]

Hello @kenteltest

Thank you for your contribution💪

I'll have a look at it

[jincod]

Hello @kenteltest

Sorry for late answer.

I've checked the solution. It looks great.

I'm thinking about 3rd step: "move sources to src directory and delete this directory after publish"

If I understand correctly we reduce the slug size but we have to restore (download) nuget packages every time. So it affect the build time. What do you think?