feat(es8): support elasticsearch v8 (#106)

add support elasticsearch v8

BREAKING CHANGE: Pelias no longer supports elasticsearch v6

This change drops support for elasticsearch v6 in order to support v8.
The current recommended version remains v7.

package.json

@@ -16,10 +16,10 @@
     "lodash": "^4.16.0",
     "minimist": "^1.2.0",
     "pelias-blacklist-stream": "^1.0.0",
-    "pelias-config": "^5.2.0",
-    "pelias-dbclient": "^2.15.0",
+    "pelias-config": "^6.0.0",
+    "pelias-dbclient": "^3.0.0",
     "pelias-logger": "^1.3.0",
-    "pelias-model": "^9.4.0",
+    "pelias-model": "^10.0.0",
     "pelias-wof-admin-lookup": "^7.8.0",
     "through2": "^3.0.0",
     "through2-filter": "^3.0.0",