Extended the NSFW's README with some use cases and regex examples

nsfw/README

@@ -6,3 +6,74 @@ Scans the message content for the string 'nsfw'
 (case insensitive) and if found replaces the content
 with a "click to open/close" link, default is closed.
 
+If you click on the 'Not safe for work' plugin under
+/settings/addon a text field appears, where you can
+extend the list of search terms. The terms must be
+seperated by commas.
+
+It is also possible to enter profile URLs as values.
+This is quite useful for the case, that you perhaps
+don't want to see postings by person_A, but person_B
+is one of your contacts and person_B used to reshare
+postings by person_A.
+
+You can also make use of regular expressions.
+They also have to be seperated by commas and the
+regex itself has to be enclosed with slashes:
+
+	... nsfw, /<REGEX>/, politics,...
+
+---------------
+A few examples:
+---------------
+
+1)
+Let's say you don't want to see postings which contain
+the term 'fake news'
+
+The term could appear in several ways:
+
+fakenews, fake news, fake_news, fake-news, f@ke news,
+f4ke news, f4k3 n3ws, and so on and so on and so on.
+
+You could write every possible version of it as single
+item into your NSFW-filter list, but this can also be
+done with a single regex, which matches all of them:
+
+	/f[@4a]k[3e][-_ ]n[3e]w[sz]/
+
+
+2)
+Another use case could be, that you are simply not
+interested in postings about christmas.
+
+	/christmas([-_ ]?(tree|time|eve|pudding))?/
+
+
+3)
+Another possibility is the usage of a so called
+'lookbehind' construct. I'll give an example followed
+by a descripton:
+
+	/(?<!the )\badvent\b/
+
+The \b is a word boundary, what matches the beginning
+and the end of a word. The simple pattern of 'advent'
+would match advent iteself, but also adventure.
+This can be prevented by
+
+	/\badvent\b/
+
+The first part if the regex above
+
+	(?<!the )
+
+is a negative lookbehind. It makes \badvent\b only
+match, if there is no 'the ' before \badvent\b or in
+words:
+
+It looks for 'advent', but doesn't match 'the advent'.
+
+
+For more informations take a look at the PCRE regex
+dialect.