ngb exemplar characters seem to be missing vowels with tilde or acute

[moyogo]

The ngb locale data has the following main character exemplar:

https://github.com/silnrsi/sldr/blob/6c4fb98a84b9eb1326b59ba6a3d7be8b76d40dcc/sldr/n/ngb.xml#L20

But the Fana Ngbangɔ 1987 (New Testament translation) by the Bible Society of the Democratic Republic of Congo seems to using the combining tilde on nasal vowels, for example:

• ã in akpã
• ẽ in ndẽ
• {ɛ̃} in ndɛ̃
• ĩ in sĩni
• {ɔ̃} in nzɔ̃
• ũ in hũngɔ

The acute accent is also used in some words:

• á in kwá
• é in sé
• {ɛ́} in tɛ́nɛ
• í in ahí
• ó in ló
• ú in adú

I may have missed a couple.

[DavidLRowe]

\u0301 and \u0303 added to main exemplar (https://github.com/silnrsi/sldr/commit/ec221476e12056b125bdb8914f55a88e7c27e38f)

Thanks!