blog post: Upload your website/dapp to mainnet through Github Actions

[vojtechsimetka]

1. PR previews

• we already solved this with gateway for dapps that are less than 10 MB

2. Production builds on master

• not fully solved
• some clues how to do this are here https://github.com/significance/swapchat2/blob/master/.github/workflows/deploy.yml#L24-L49
• there may be other considerations with postage stamps etc but we do not necessarily want to solve it now
• either in the blog post or in the documentation add further postage stamps explanation - what is amount, what is depth, how it relates to size that can be uploaded, time for the content to be in the network and the price in xBZZ