update querybuilder readme

Author: LeandroSNunes

querybuilder/README.md

@@ -1,2 +1,65 @@
-# querybuilder
-Package for jQuery Query Builder Rule Evaluator
+# Query Builder
+This package is a Golang Rule Evaluator for [jQuery QueryBuilder](https://querybuilder.js.org/index.html)
+
+You will use the Evaluator to check if a dataset matches the JSON rules produced by the jQuery QueryBuilder plugin.
+Dataset is a map of the type `map[string]interface{}`
+You can access nested fields with a dot notation. e.g. fields.Question to access {'fields' => {'Question' => 'Answer'}}
+
+## Example usage
+
+```golang
+
+var rulesetJSON = `{
+  "condition": "AND",
+  "rules": [
+    {"id": "name", "field": "name", "type": "string", "input": "text", "operator": "begins_with", "value": "shirt"},
+    {"id": "category", "field": "category", "type": "string", "input": "text", "operator": "equal", "value": "woman"},
+    {"condition": "OR","rules": [
+      {"id": "price", "field": "price", "type": "double", "input": "text", "operator": "greater","value": 10.50},
+      {"id": "published_at", "field": "published_at", "type": "date", "input": "text", "operator": "less", "value": "2019-12-25"}
+      ]}
+    ]}`
+
+var datasetJSON = `{"name": "short sleeve shirt", "category": "woman", "price":  33.0, "published_at": "2020-1-1"}`
+
+func main(){
+  var ruleset map[string]interface{}
+  var dataset map[string]interface{}
+  json.Unmarshal([]byte(rulesetJSON), &ruleset)
+  json.Unmarshal([]byte(datasetJSON), &dataset)
+  
+  qb := querybuilder.New(ruleset)
+  if qb.Match(dataset) {
+    fmt.Println("√ dataset is valid!")
+  }
+}
+
+```
+
+## Operators
+All the default operators have been implemented, see in `/operators` folder
+You can easily add custom operators, see:
+
+```golang
+import "github.com/enjoei/pkg/querybuilder/operator"
+
+func init() {
+	AddOperator(EqualsFive)
+}
+
+// Equal
+var EqualsFive = &Operator{
+	Name: "equals_five",
+	Evaluate: func(input, value interface{}) bool {
+		return input(int) == 5
+	},
+}
+```
+The Evaluate function shoult receive a input and value params, even if a value is not required
+
+## Contributing
+- Fork it
+- Create your feature branch (`git checkout -b my-new-feature`)
+- Commit your changes (`git commit -am 'Add some feature'`)
+- Push to the branch (`git push origin my-new-feature`)
+- Create new Pull Request