create_golem should advise to install dev_dependencies if there are not all here

[ColinFay]

Validation

• [ ] If I uninstall some dev dependencies and create a golem, a message is printed to the console advising to install them.

Dev - Tech

When launching the creation of a golem app, we should check for dev dependencies and suggest to install them if any is missing

• [ ] In R/create_golem.R:
  • [ ] loop over the dev deps and check rlang::is_installed
  • [ ] if any is not true, print a message to the console

Estimated time

0h30

• [ ] Add the estimate as a comment with /estimate
• [ ] When I close the issue, I've written the time spent solving this issue, using /spent

[ColinFay]

/estimate 30m

[ColinFay]

Done in #966