Add style guideline about anchor text

Not preferred:

```
Do the thing :ref:`on the settings menu `.
```

Preferred:

```
:ref:`Do the thing `.

If context is needed:

:ref:`Do the thing ` on the :ref:`settings menu `.
```

Not prefered:

```
You can do a thing. `Learn more in this tutorial. `_.
```

Prefered:

```
`You can do a thing `_.
```

------

(Actual style guide should use realish examples, not "do a thing".)

Guidance should probably mention that it isn't *always* reasonable to follow this rule,
but to do so whenever you can.

Locate the actual style guide in the documentation and review any existing guidance about anchor or link text first. Add real examples covering the preferred patterns and note that the rule is flexible when needed; the work is done when the guidance is clear and examples reflect the issue's recommendations.

Written by the indexing model from the issue text.