all: add postgres to docs

Reviewed By: alexsn

Differential Revision: D18245079

fbshipit-source-id: d4f59d88fe2125d924bfb85521fa43898ea5ce35

doc/md/crud.md

@@ -36,6 +36,28 @@ func main() {
 }
 ```
 
+**PostgreSQL**
+
+```go
+package main
+
+import (
+	"log"
+
+	"<project>/ent"
+
+	_ "github.com/lib/pq"
+)
+
+func main() {
+	client, err := ent.Open("postgres","host=<host> port=<port> user=<user> dbname=<database> password=<pass>")
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer client.Close()
+}
+```
+
 **SQLite**
 
 ```go

doc/md/dialects.md

@@ -8,6 +8,12 @@ title: Supported Dialects
 MySQL supports all the features that are mentioned in the [Migration](migrate.md) section,
 and it's being tested constantly on the following 3 versions: `5.6.35`, `5.7.26` and `8`. 
 
+
+## PostgreSQL
+
+PostgreSQL supports all the features that are mentioned in the [Migration](migrate.md) section,
+and it's being tested constantly on the following 3 versions: `10`, `11` and `12`. 
+
 ## SQLite
 
 SQLite was developed only for testing, and it does not support the incremental updates for tables.