Merge pull request #370 from SiaFoundation/release

chore: prepare release 0.20.0

Merge pull request #355 from SiaFoundation/release

chore: prepare release 0.19.0

Merge pull request #339 from SiaFoundation/release

chore: prepare release 0.18.7

Merge pull request #337 from SiaFoundation/release

chore: prepare release 0.18.5

Merge pull request #330 from SiaFoundation/release

chore: prepare release 0.18.4

Merge pull request #328 from SiaFoundation/release

chore: prepare release 0.18.3

Merge pull request #322 from SiaFoundation/release

chore: prepare release 0.18.2

Merge pull request #319 from SiaFoundation/release

chore: prepare release 0.18.1

Merge pull request #308 from SiaFoundation/release

chore: prepare release 0.18.0