chore(dependencies): pin dependency microbundle to 0.12.0-next.8
chore(dependencies): pin dependency microbundle to 0.12.0-next.8

stencila/stencila,stencila/stencila,stencila/stencila,stencila/stencila,stencila/stencila,stencila/stencila,stencila/stencila