Experimental language change tests

[gautierchomel]

As discussed during group call, January 16, 2024.
This adds, at the root, one folders named language_change with three files files:

• test for language change iso 639-1 without country code (i.e. two letters only)
• test for language change iso 639-1 with country code (i.e. four letters)
• test for language change iso 639-2 without country code (i.e. three letters)

[clapierre]

@gautierchomel
I downloaded your pull request but bringing up these html files in Edge, I am getting the following error messages

This page contains the following errors:
error on line 13 at column 142: Opening and ending tag mismatch: h1 line 13 and h2
Below is a rendering of the page up to the first error.

[gautierchomel]

@clapierre, strange but true. It's fixed now.

[clapierre]

Here were the results I found, but I am not an expert here in this.
With
NVDA when I switch to eSpeak NG I get the following results:
(main language code EN / FR): Switches correctly
(Sub language code EN-US / FR-CA): Switches correctly
(3 letter main language code, fra ) : Does not switch languages

NVDA with other voices like Windows OneCore Voices or Microsoft Speech API version 5
Nothing switched, but maybe I need to install additional voices to allow for this.

JAWS with Eloquence all 3 tests pass, all other language options nothing switched correctly. eg. Microsoft Mobile (factory) or SAPI 5x (Factory)

Voice Over on my Mac. I was not able to get any of the 3 to switch I had both English and French set up in voice over and had it to "automatically switch based on language detected.