Document how to use distinct query analyzer with Lucene

[line-o]

Before eXist-db/exist#2991 - or respectively eXist-db/exist#3227 - is merged:

https://exist-db.org/exist/apps/doc/lucene, the article covering the integration of Lucene in exist-db, should be extended with a section.
It should describe one or two use-cases for having one analyzer for indexing and another to analyze the query.

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[duncdrum]

usually we add documentation before changes are merged in the main repo. The additions sound like a good idea.

[line-o]

Possible use-cases:

• Sanskrit analyzer -> lenient mode
• Index with WhitespaceAnalyzer, query with a Language specific one
• Index with GermanAnalyzer without stopwords query with and without stopwords

[sten1ee]

Here - I've fixed you some documentation for that feature:
#445

[sten1ee]

The above mentioned docs PR#445 was approved and merged,
@line-o resolve this, willya?