feat: assertions rules (#489)

Co-authored-by: Anastasiia <anastasiia@redocly.com>
Co-authored-by: Adam Altman <adam@redoc.ly>
Co-authored-by: Ivana Isadora Devcic <33730345+skadinna@users.noreply.github.com>

__tests__/lint/assertions-max-length-array-error/snapshot.js

@@ -0,0 +1,32 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`E2E lint assertions-max-length-array-error 1`] = `
+
+validating /openapi.yaml...
+[1] openapi.yaml:22:9 at #/paths/~1pet~1findByStatus/get/tags
+
+Operation tags should have maximum 2 items
+
+20 | summary: summary example
+21 | tags:
+22 |   - foo
+   |   ^^^^^
+23 |   - baz
+   |   ^^^^^
+24 |   - bar
+   |   ^^^^^
+25 | responses:
+   | ^
+26 |   '200':
+27 |     description: example description
+
+Error was generated by the assertion #1 rule.
+
+
+/openapi.yaml: validated in <test>ms
+
+❌ Validation failed with 1 error.
+run \`openapi lint --generate-ignore-file\` to add all problems to the ignore file.
+
+
+`;