newrule(iframe_interactive_tabbable) Iframe with interactive content should not be excluded from tab order using tabindex

[shunguoy]

newrule(iframe_interactive_tabbable) Iframe with interactive content should not be excluded from focus order using tabindex

• New Rule(s): List rule IDs. iframe_interactive_tabbable.ts
• New or modified help files: List rule IDs. iframe_interactive_tabbable.html

This PR is related to the following issue(s):

#1154 #1283

Testing reference:

https://wai-wcag-act-rules.netlify.app/standards-guidelines/act/rules/akn7bn/proposed/#visible
or
test/v2/checker/accessibility/rules/iframe_interactive_tabbable_ruleunit/*

I have conducted the following for this PR:

• I validated this code in Chrome and FF
• I validated this fix in my local env
• I provided details for testing
• This PR has been reviewed and is ready for test
• I understand that the title of this PR will be used for the next release notes.

[philljenkins]

mostly similar files as PR #1306. But 1306 has a couple later updates for example in element_scrollable_tabbable.html

[ErickRenteria]

Validated