add doc on searching and filtering

Author: mbalunovic

docs/explorer/How-To-Guide/search_and_filter.md

@@ -0,0 +1,30 @@
+# Search
+
+Often, there is a large number of traces in the dataset. In this section, we describe how to search over these traces efficiently
+and filter them according to different criteria.
+
+### Exact search
+
+Any text put in the search box, including spaces, is searched for exactly (but case-insensitively) in the trace.
+
+### Filters
+
+Separately from exact search, any white-space-separated token containing a `:` is interpreted as a filter. 
+There are several types of filters:
+
+- `is:annotated`
+    - filters for traces with annotations
+- `not:annotated`
+    - filters for traces without annotations
+- `meta`
+    - searches for traces with the corresponding metadata
+    - attribute is a string identifying one of the attributes in the meta data (**case sensitive**)
+    - operator is one of
+        - `=`, `==` - exact match
+            - e.g. `meta:title=foo`
+        - `<` , `>`, `<=` , `>=` - numerical comparison
+            - e.g. `meta:tests_passed>3`
+        - `%` - string containment
+            - e.g. `meta:title%react`
+- `is:invariant`
+    - groups traces by type of error detected by the invariant analyzer