Repository: prettier/prettier (JavaScript)

Issue:
Improve GraphQL union types formatting
I think we can make consistency for printing union types (`|`) between TS and Gql. What do you think?

**Prettier 2.8.3**
[Playground link](https://prettier.io/playground/#N4Igxg9gdgLgprEAuEBXKBLaACAynAQwCcwALAJTgGdUAbGbAXgB0oAfbAYWgDM4iEYOBwBi1GBgBuBWtg7coQogw4A1BKjhyuvfoOHYxVCdNnzoSldnVRNrEABoQEAA4ToVZKGJEIAdwAFYgRPFBk-AgBPTycAIyICMABrOBhcAgBbOAAZDCg4ZB4ZKjg4hOTU3BdEvIBzZBgiTSc4DNi4ABMOzuyCKFrUAlq4EQgiDIIYCX7kEAJUGAhHEFIYDNoAdVIMeCpqoXwoKh2pHcjZsCoYkDyS5QCE2onC4tKQACsqAA9cOto4ACKqAg8BetBKTmqRDus1qCRcpAAjrRli4iHkYBsMB0YKRkAAOAAMkN8JQ28NmaOo-EkBSciOB8AerlCcyoAFp8p1OssBAyMAIHkNnkgiuC3iUMhgGk0JX84ABBKbo2ILOABfi5fJgiEgY79f5AkEFUWvJwwAixLE4vFIABM5oSGFodW4GRFIGoAFZlqgSgAVS2hMW6ySaACSUG6sFwYHRbgVUdwMEi-x1cAAvhmgA)
<!-- prettier-ignore -->
```sh
--parser graphql
```

**Input:**
<!-- prettier-ignore -->
```graphql
union SearchResult = Conference| Festival | Concert | Venue | Conference| Festival | Concert | Venue

```

**Output:**
<!-- prettier-ignore -->
```graphql
union SearchResult =
    Conference
  | Festival
  | Concert
  | Venue
  | Conference
  | Festival
  | Concert
  | Venue

```

**Expected behavior:**

```graphql
union SearchResult =
  | Conference
  | Festival
  | Concert
  | Venue
  | Conference
  | Festival
  | Concert
  | Venue

```


Hints:
HI @sosukesuzuki - can you please assigned this to me ? this will be my first contribution to prettier library :) 
@ArchitGajjar Go ahead!
@sosukesuzuki - I made some changes and execute below commands.

> yarn build:website

> cd website/playground

> npm run start

Here, I'm seeing my changes are not reflected in playground when I test. 

How do you verify your changes are reflected while testing into local ? 
```
$ touch test.js
$ yarn debug test.js
```

Patch:
diff --git a/src/language-graphql/printer-graphql.js b/src/language-graphql/printer-graphql.js
--- a/src/language-graphql/printer-graphql.js
+++ b/src/language-graphql/printer-graphql.js
@@ -384,7 +384,7 @@ function genericPrint(path, options, print) {
                 " =",
                 ifBreak("", " "),
                 indent([
-                  ifBreak([line, "  "]),
+                  ifBreak([line, "| "]),
                   join([line, "| "], path.map(print, "types")),
                 ]),
               ]


Test patch:
diff --git a/tests/format/graphql/union-types/__snapshots__/jsfmt.spec.js.snap b/tests/format/graphql/union-types/__snapshots__/jsfmt.spec.js.snap
--- a/tests/format/graphql/union-types/__snapshots__/jsfmt.spec.js.snap
+++ b/tests/format/graphql/union-types/__snapshots__/jsfmt.spec.js.snap
@@ -16,6 +16,8 @@ union myThirdUnion = AVeryVeryVeryLongNamedTypeName | ASecondVeryVeryVeryLongedN
 
 union longUnion = A | B | C | D | E | F | G | H | I | J | K | L |  A | B | C | D | E | F | G | H | I | J | K | L
 
+union SearchResult = Conference| Festival | Concert | Venue | Conference| Festival | Concert | Venue
+
 # comment
 # comment2
 union union = B | C | D
@@ -23,17 +25,17 @@ union union = B | C | D
 union myUnion = ATypeName | ASecondTypeName
 
 union tooLongNameeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee =
-    A
+  | A
   | B
 
 union mySecondUnion = ATypeName | ASecondTypeName | AThirdTypeName
 
 union myThirdUnion =
-    AVeryVeryVeryLongNamedTypeName
+  | AVeryVeryVeryLongNamedTypeName
   | ASecondVeryVeryVeryLongedNameTypeName
 
 union longUnion =
-    A
+  | A
   | B
   | C
   | D
@@ -58,6 +60,16 @@ union longUnion =
   | K
   | L
 
+union SearchResult =
+  | Conference
+  | Festival
+  | Concert
+  | Venue
+  | Conference
+  | Festival
+  | Concert
+  | Venue
+
 # comment
 # comment2
 union union = B | C | D
diff --git a/tests/format/graphql/union-types/union_types.graphql b/tests/format/graphql/union-types/union_types.graphql
--- a/tests/format/graphql/union-types/union_types.graphql
+++ b/tests/format/graphql/union-types/union_types.graphql
@@ -8,6 +8,8 @@ union myThirdUnion = AVeryVeryVeryLongNamedTypeName | ASecondVeryVeryVeryLongedN
 
 union longUnion = A | B | C | D | E | F | G | H | I | J | K | L |  A | B | C | D | E | F | G | H | I | J | K | L
 
+union SearchResult = Conference| Festival | Concert | Venue | Conference| Festival | Concert | Venue
+
 # comment
 # comment2
 union union = B | C | D
\ No newline at end of file