feat(CI): test caller-pays-for-query truffle example in CI

[gskapka]

...per title.

[D-Nice]

merging if tests pass

[gskapka]

merging if tests pass

Build is failing

I chuckled. More so when I looked and it's not this new example causing the failure, it's good old pesky url-requests.

I have zero clue now why the computation datasource in that example occasionally returns nothing from the POST, and that fix I pushed to that clearly hasn't solved the intermittent issue. We should probably drop it from the CI (again) and go back to the drawing board re that particular example.

This new Truffle example however should be absolutely fine in the CI, and it passed here with flying colours.

[gskapka]

Have removed that last commit re-enabling the intermittently failing url-request test, and forced the branch. Better this way then ending up with two commits in master where the second just undoes the first.

☢️ Branch forced - please re-pull.

This way this PR can be merged and closed, and I've created a new issue re the url-requests so we can deal with that separately instead.

Let me know if this PR and the process above both LGTY @D-Nice and we can get this merged.

[D-Nice]

LGTM merging