added csvgrep

pages/common/csvgrep.md

@@ -0,0 +1,16 @@
+# csvgrep
+
+> Filter CSV rows with string and pattern matching.
+> Included in csvkit.
+
+- Find rows that have a certain string in column 1:
+
+`csvgrep -c {{1}} -m {{string_to_match}} {{data.csv}}`
+
+- Find rows in which columns 3 or 4 matches a certain regex pattern:
+
+`csvgrep -c {{3,4}} -r {{regex_pattern}} {{data.csv}}`
+
+- Find rows in which the "name" column does NOT include the string "John Doe":
+
+`csvgrep -i -c {{name}} -m {{"John Doe"}} {{data.csv}}`