Docs: placeholder text in terminal commands can be confusing

Problem to solve

We have many cases where we need to display some placeholder text in a command. For example, an email, a username, a token, etc.

So far, we've been using the notation <your_email>, <your_username>, <your_access_token>. Sometimes, we use a fake value, but we have kinda standardized with <your_something>.

While this is much better than using a fake value, the special characters <> can be confusing to a user, are they part of the command or no? We should do something to clarify this.

Proposal

Use simple text with no special symbols, like the DigitalOcean guide https://www.digitalocean.com/docs/style/language/#stand-in-variables.

Use use_your_<variable> with in-line code formatting when indicating when the user should substitute their own value in a command. For example, use_your_droplet_ip or use_your_domain.

Who can address the issue

@gl-docsteam