style: add syntax highlighting to pql examples

Author: ayZagen

content/en/api/core/03.query-syntax.mdoc

@@ -9,7 +9,8 @@ layout:
     <section>
         <h1>PlusAuth Query Language Reference</h1>
 
-PlusAuth provides its own [CQL](https://wikipedia.org/wiki/Contextual_Query_Language) for querying over resources in an easy way. It will be referred as **PQL (PlusAuth Query Language)** in PlusAuth documentation.
+PlusAuth provides its own [CQL](https://wikipedia.org/wiki/Contextual_Query_Language) for querying over resources in an easy way.
+ It will be referred as **PQL (PlusAuth Query Language)** in PlusAuth documentation.
 
 Common features and characteristics of PQL are as following:
 
@@ -19,17 +20,30 @@ Common features and characteristics of PQL are as following:
 4. Supports nested properties ( `profile.name`, `metadata.color`, .etc)
 5. Field grouping ( `profile[given_name = "John" AND family_name = "Doe" ]` )
 
-Below, you can find more examples and detailed descriptions of PQL.
-
+Below, you can find more examples and detailed characteristics explanations of PQL.
+
+## Values
+**Booleans**, **numbers** and **null** do not need any wrapping whereas all other values must be wrapped with **double quotes**.
+Example values:
+```lua
+null
+true
+false
+1
+0
+-1
+"string"
+"sentence with space"
+```
 ## Common operators
 
-You can check equality, greatness and matching value in a list of values. Here is a sample query for retrieving users whose email is verified.
-```
+You can check equality, greatness and matching value in a list of values. Here is a sample query for retrieving entities whose email is verified.
+```lua
 email_verified = true
 ```
 
-For retrieving users whose email is NOT verified, you can use not equal operator
-```
+For retrieving entities whose email is NOT verified, you can use not equal operator
+```lua
 email_verified != true
 ```
 
@@ -39,37 +53,39 @@ You can use greater than (**\>**), less than (**&lt;**), greater or equal (**\>=
 
 In some cases you may need to have more than one condition to apply for retrieving your resources. You can use **AND**,**OR** for this purpose.
 
-Let's retrieve users whose email is "johndoe@johndoe.club" or whose email is not verified. Here is the query:
-```
+Let's retrieve entities which has `email` as `johndoe@johndoe.club` or which has `email_verified` field set to `false`. Here is the query:
+```lua
 email = "johndoe@johndoe.club" OR email_verified != true
 ```
 
 You can also group statements. Just wrap your condition with parentheses. Here is an example:
-```
+```lua
 (profile.given_name = "Jane" AND profile.family_name != "Doe") OR email_verified = true
 ```
 
 ## Match value in a list of values
 
 For checking value from a defined list of values PQL provides **IN** operator. You can provide list of values being separated by commas.
-```
+```lua
 profile.given_name IN "John","Jane"
 ```
 
-The query above will retrieve users whose given name is either "John" or "Jane"
+The query above will retrieve entities whose given name is either "John" or "Jane"
 
 ## Pattern matching
 
 `ILIKE` operator can be used for queries that are data based on pattern-matching techniques. Its result includes strings that are case-insensitive and follow the mentioned pattern.
+
 An underscore (`_`) in pattern stands for (matches) any single character; a percent sign (`%`) matches any sequence of zero or more characters.
 
-Some examples for a user with name `abc`:
+Some examples for a entity with name `abc`:
 
-```
-name ILIKE 'abc'  => true
-name ILIKE 'a%'   => true
-name ILIKE '_b_'  => true
-name ILIKE 'c'    => false
+```lua
+name ILIKE "abc"  --> true
+name ILIKE "a%"  --> true
+name ILIKE "_b_"  --> true
+name ILIKE "ab"   --> false
+name ILIKE "bc"   --> false
 ```
 
 `ILIKE` pattern matching always covers the entire string. Therefore, if it's desired to match a sequence anywhere within a string, the pattern must start and end with a percent sign.