feat(search): add search filter doc

docs/search.md

@@ -38,3 +38,70 @@ There, you can edit or remove any filter/search your created!
 In this user zone, you can set a default filter (preset filters or your own).
 
 > Pro Tip: this is saved in your user preference. It means that you can connect anywhere on any browser, you'll find your preference.
+
+## Filter syntax
+
+> A filter allows you to search through a collection of objects which have multiple properties and may even contains other nested objects.
+
+#### Searching for a string (or substring)
+
+Simply write the string, if it contains special characters just surround it with quotes:
+
+- `simple-string`
+- `"string with special characters like whitespaces"`
+
+> The search is recursive, case insensitive and non-anchored (i.e. matches if the pattern is contained in a string).
+
+#### Searching a specific property
+
+Write the property name, followed by a colon `:` and a subfilter:
+
+- `name_label:"my VM"`
+- `virtualizationMode:hvm`
+- `boot:order:cn`
+
+#### Negation
+
+Prefix your filter with an exclamation mark `!`:
+
+- `!hvm`
+- `!power_state:Running` or `power_state:!Running`
+
+#### Intersection
+
+Simply write filter's terms side by side:
+
+- `power_state:Halted !virtualizationMode:hvm`
+
+#### Grouping
+
+Parentheses can be used to group terms together:
+
+- `!(power_state:Running virtualizationMode:hvm)`
+
+#### Union
+
+Pipe `|` followed by a group of terms:
+
+- `|(vm1 vm2)`
+- `power_state:|(Running suspended)`
+
+#### Truthy property
+
+This one is less common but can be used to check whether a property has a truthy value (`true`, non-empty string or non-zero number).
+
+Postfix the name of a property by an question mark `?`:
+
+- `auto_poweron?`
+- `high_availability?`
+
+## Available properties
+
+No documentation on this side either, but you can see all objects and their properties using `xo-cli --list-objects`.
+
+Take a look at [the documentation](https://github.com/vatesfr/xen-orchestra/tree/master/packages/xo-cli#xo-cli) :)
+
+For the Xen Tools status:
+
+- `xenTools?`: whether the tools are installed
+- `xenTools:"up to date"`: whether they are installed and up to date