Add contract suspension worked example

[duncandewhurst]

Closes #758

As well as adding the worked example, I added a note to Contract status on codelists.md as that seems like the most proximate place to signpost publishers and users to the example.

Once agreed, we can add this example to the statusDetails extension documentation for OCDS 1.1.

[duncandewhurst]

@yolile @jpmckinney this worked example only addresses contract suspension, not suspended tenders (#430). Do you think we should have a separate worked example for suspended tenders, or try to have one worked example that applies to both contract suspension and suspended tenders, or can we do without a suspended tenders example given that the concept only came up once, so far?

[jpmckinney]

In #430, I'm not clear how a process can be suspended/blocked prior to the award stage.

Besides courts, #430 mentions "blocked by the decision of Deposit Guarantee Fund commission", but we don't have a full example of either. So, we can't do a worked example.

After the award stage, it's common for the signing of a contract to be blocked during a standstill period, where tenderers challenge the award on specific grounds. I added a comment to #1142 about adding a worked example for that scenario.

This PR is ready for a first review.

[mrshll1001]

I can't spot any typos or errors, and the expected files are changed/introduced.

[jpmckinney]

I fixed conflicts and made one commit.

[jpmckinney]

I've created the follow-up issue for the extension: open-contracting/ocds-extensions#168

After merging, please manually close #758. Since 1.2-dev is not the default branch, GitHub will not close it automatically.