Could README instruction have more details?

[catcatcatcat]

Dear Mermaid Team,

Thank you for the wonderful editor in advance, I love to use mermaid online editor.

My issue is a novice problem.

Sometimes I have no internet connection and cannot use it, in a previous issue #217
mermaid-js/mermaid#217
I saw one of the solutions is run it locally, but I failed in the very first step yarn install with an error msg: "-bash: yarn: command not found".

I am a non-programmer and have little knowledge about what's going on,
after I asked my friend, I tried: npm install yarn and run yarn install again with + yarn@1.16.0 but still saw the same error msg.

Then I tried brew install yarn and finally succeeded with yarn install v1.17.0

I think it would be kind if README pointed out you have to install yarn before type yarn install and it would be kinder if add how to install yarn section.

How do you think about it? Thank you so much.

[morgen-peschke]

For anyone who stumbles on this issue, the project has been moved and the new one includes a docker image you can spin up locally to get an offline editor.

See: https://github.com/mermaid-js/mermaid-live-editor#run-published-image

[catcatcatcat]

Thank you for replying!