Use `<b>` instead of `<strong>` to format UI text

[eric-schneider]

When referring to text-only UI elements and buttons, we typically style these named elements using bold formatting. Rightly or wrongly, AsciiDoc maps bold formatting onto the <strong> HTML element:

In the *IP Access List* section, click *Export List*.

<p>In the <strong>IP Access List</strong> section, click <strong>Export List</strong>.</p>

Unfortunately, this usage runs afoul of the GDDSG:

The reason for using the b element is that in modern HTML, b connotes text to which you want to draw visual attention, whereas the strong element indicates strong importance.

(NOTE: This is not an issue for UI text associated with an icon. The icon: and svg: macros already apply <b> instead of <strong> to button text.)

Possible solution

One possible solution might be to use AsciiDoc's Button and Menu UI Macros. By default, these macros apply the <b> tag and also apply the CSS classes button and menuref respectively:

In the menu:IP Access List[] section, click btn:[Export List].

<p>In the <b class="menuref">IP Access List</b> section, click <b class="button">Export List</b>.</p>

[eric-schneider]

This issue may be affected by #150.