ci: drop node 8, adopt node 12 (karma-runner#3430)

BREAKING CHANGE: no more testing on node 8.

.travis.yml

@@ -1,8 +1,8 @@
 sudo: false
 language: node_js
 node_js:
-  - 8
   - 10
+  - 12
 
 env:
   global:
@@ -13,7 +13,7 @@ matrix:
   fast_finish: true
   include:
     - name: "Lint code and commit message format"
-      node_js: "8"
+      node_js: "10"
       env: VALIDATE_COMMIT_MSG=true LINT=true
 
 before_install:
@@ -47,7 +47,7 @@ script:
 
 after_success:
   # run automated release process with semantic-release
-  - if [[ "$TRAVIS_BRANCH" == "master" && "$TRAVIS_EVENT_TYPE" == "push" && "$TRAVIS_NODE_VERSION" == "10" ]]; then
+  - if [[ "$TRAVIS_BRANCH" == "master" && "$TRAVIS_EVENT_TYPE" == "push" && "$TRAVIS_NODE_VERSION" == "12" ]]; then
       npm i --no-save semantic-release@15 @semantic-release/changelog@3 @semantic-release/git@7;
       semantic-release;
     fi;

appveyor.yml

@@ -2,8 +2,8 @@ version: "{build}"
 
 environment:
   matrix:
-    - nodejs_version: "8"
     - nodejs_version: "10"
+    - nodejs_version: "12"
 
 matrix:
   fast_finish: true

package.json

@@ -475,7 +475,7 @@
     "karma": "./bin/karma"
   },
   "engines": {
-    "node": ">= 8"
+    "node": ">= 10"
   },
   "version": "4.4.1",
   "license": "MIT",