Search with case insensitiveness

[feugy]

What's in there?

As for #11, we would like so search for values regardless of their case.
This adds

• a new caseInsensitive option to search() method (default behave as it used to).
• documentation
• changelog update (version 2 wasn't released yet)

Notes to reviewers

Writing

const op = caseInsensitive ? 'ILIKE' : 'LIKE'
if (who) sql.append(SQL` AND who_id ${op} ${exactMatch ? who : '%' + who + '%'}`)

Does not work, because op is treated as a parameter and escaped, leading to incorrect query (error is: syntax error at or near "$3")

Unfortunately, the .append() method of our SQLStatements object does not allow plain strings (as opposed to this library), leading to this convoluted syntax:

if (who) sql.append(SQL([` AND who_id ${op} `])).append(SQL`${exactMatch ? who : '%' + who + '%'}`)

[ShogunPanda]

LGTM!