drops node10 test/build in CI

Since we are transpiling Kiln on release we probably don't need to
guarantee the ability to build with Node10 (which is EOL in a few
months). Removing that build compatability requirement will allow us to
use `string.prototype.matchAll` (needed for link validation).

The alternative would be to add another dependency or come up with our
own implementation in the short term.

All current major browsers support `.matchAll` so it's not worth the
hassle IMO.

.circleci/config.yml

@@ -28,24 +28,6 @@ general:
     - coverage
 
 jobs:
-  test_node10:
-    docker:
-      - image: node:10
-    working_directory: ~/repo
-    steps:
-      - checkout
-      - restore_cache:
-          keys:
-          - v2-node10-dependencies-{{ checksum "package.json" }}
-          - v2-node10-dependencies-
-      - run: npm install
-      - save_cache:
-          paths:
-            - node_modules
-          key: v2-node10-dependencies-{{ checksum "package.json" }}
-      - run: npm test -- --maxWorkers=4
-      - run: npm run build
-
   test_node12:
     docker:
       - image: node:12
@@ -87,8 +69,6 @@ workflows:
   version: 2
   test:
     jobs:
-      - test_node10:
-          <<: *filter_all
       - test_node12:
           <<: *filter_all
       - test_node14: