When I type the string string "cli", I get results like "client 1", "client 2", etc. But when I type "lie", I dont get any results. It seems that wild cards are added only at the end.
How do add this feature to my site?
It's not supported by ZCTextIndex, see http://docs.zope.org/zope2/zope2book/SearchingZCatalog.html#searching-zctextindexes
I fear that also switching to search using Solr (through collective.solr or other integrations) will not help.
Products.TextIndexNG3 (https://pypi.python.org/pypi/Products.TextIndexNG3) supports wildcards at the beginning and much more.
it's even possible to define synonyms yourself - so a search for 'kitten' also returns documents containing 'cat'
works fine for plone4.x, didn't try for plone5. and as @keul mentioned there is not much development going on for this addon too because the trend is to use specialized search-services