improve nilakkhana UID to acronym for Vinaya

[sujato]

For nilakkhana links we use a shorthand:

[mn123:4.5]()

Which is transformed to (more or less):

<a href='https://suttacentral.net/en/sujato/mn123#4.5'>MN 123:4.5</a>

To change the UID mn to the acronym MN we use the following list:

https://github.com/suttacentral/bilara-data/blob/published/.nilakkhana/uid_to_acro.py

Also see:

https://github.com/suttacentral/bilara-data/blob/published/.nilakkhana/test_uid_to_acro.py

However this does not handle the complex cases found in the Vinaya. So we should add and test the following.

"pli-tv-bu-vb-pj": "Bu Pj", 
"pli-tv-bu-vb-ss": "Bu Ss", 
"pli-tv-bu-vb-ay": "Bu Ay", 
"pli-tv-bu-vb-np": "Bu NP", 
"pli-tv-bu-vb-pc": "Bu Pc", 
"pli-tv-bu-vb-pd": "Bu Pd", 
"pli-tv-bu-vb-sk": "Bu Sk", 
"pli-tv-bu-vb-as": "Bu As", 
"pli-tv-bi-vb-pj": "Bi Pj", 
"pli-tv-bi-vb-ss": "Bi Ss", 
"pli-tv-bi-vb-np": "Bi NP", 
"pli-tv-bi-vb-pc": "Bi Pc", 
"pli-tv-bi-vb-pd": "Bi Pd", 
"pli-tv-kd": "Kd", 
"pli-tv-pvr": "Pvr",