Add support for @stem.sameas

[o-sapov]

@stem.sameas is a new MEI attribute for single stem voices. Cf. the MEI discussion here.

Here is an example.

W. A. Mozart, Neue Mozart Ausgabe, K. 551/01, m. 9, oboi, fagotti & corni

Click to see the MEI file.

```xml Oboi Fagotti Corni in Do/C

```

In presence of @artic, only one articulation per note pair should be shown. Note the <supplied>/@sameas reference.

W. A. Mozart, NMA, K. 543/01, m.70, clarini

Click to see the MEI file.

```xml Clarini in Mi♭/Es

```

[lpugin]

Example added to the test-suite https://github.com/rism-digital/verovio.org/commit/4eb960beaf1ccd756df356bf087d048efeb93a90

[lpugin]

Regarding the articulation signs I can see the some orchestral scores have it on both notes

I think this needs to be clarified in MEI first. Any thoughts?

Your example with <supplied> is a bit complex to start with because the fact the articulation is supplied has nothing to do with stem.sameas. Could you give an example with the articulation not being supplied? I think that in any case the @sameas should be on an<artic> and not on <supplied>. (Also, my understanding of <supplied> is that is should only be used with <choice>.)

[craigsapp]

NB: this example answers my questions about is the double-articulation style used in orchestral scores. Maybe it would be useful to have a verovio option to merge or ignore sameas articulations? And possibly this option could be added to scoreDef/staffDef...

[lpugin]

Implemented https://github.com/rism-digital/verovio/pull/2596