Added $leftJoinRelation (#182)

* Update index.js

* Update index.js

* Revert "Update index.js"

This reverts commit 108df4f.

* Revert "Update index.js"

This reverts commit aed25fb.

* Added $leftJoinRelation

* Fixed a bug

Fixed the issue in _find count when both $joinRelation and $leftJoinRelation are in the query.

* Updated README file

* Remove redundant if conditions

* Added test

* Delete .vscode directory

* Fixed the failed test

Fixed the two failed tests.

* Fixed the new test that failed postgresql

* Apply ESLint

* Apply ESLint

---------

Co-authored-by: Dekel Barzilay <[email protected]>

Author: wz5899

.gitignore

@@ -32,6 +32,7 @@ db.sqlite
 data.db
 .idea
 .nyc_output
+.vscode/settings.json
 
 # Tern
 .tern-port

README.md

@@ -180,7 +180,11 @@ Note that all this eager related options are optional.
   [`withGraphFetched`](https://vincit.github.io/objection.js/api/query-builder/eager-methods.html#withgraphfetched) documentation.
 
 - **`$joinRelation`** - filter based on a relation's field. use with `$eager` to also fetch the relation. See
-  [`joinRelated`](https://vincit.github.io/objection.js/api/query-builder/join-methods.html#joinrelated)
+  [`joinRelated`](https://vincit.github.io/objection.js/api/query-builder/join-methods.html#joinrelated) 
+  documentation.
+  
+- **`$leftJoinRelation`** - filter based on a relation's field using LEFT JOIN. use with `$eager` to also fetch the relation. See
+  [`leftJoinRelated`](https://vincit.github.io/objection.js/api/query-builder/join-methods.html#leftjoinrelated)
   documentation.
 
 - **`$joinEager`** - filter based on a relation's field. See