Add BuildKit and docker manifest command. close #390 ,close #391

Signed-off-by: khs1994 <khs1994@khs1994.com>

.travis.yml

@@ -1,7 +1,8 @@
 language: bash
-sudo: required
+
 services:
 - docker
+
 before_install:
 - openssl aes-256-cbc -K $encrypted_6cc8cff04075_key -iv $encrypted_6cc8cff04075_iv
   -in .travis/id_rsa.enc -out ~/.ssh/id_rsa -d
@@ -10,8 +11,10 @@ before_install:
 - date
 - git config --global user.name "khs1994"
 - git config --global user.email "khs1994@khs1994.com"
+
 script:
 - docker run -it --rm -v $PWD:/srv/gitbook-src yeasy/docker_practice build
+
 after_success:
 - sudo chmod -R 777 _book
 - echo "FROM nginx:1.13.8-alpine" >> Dockerfile
@@ -29,14 +32,17 @@ after_success:
 - COMMIT=`date "+%F %T"`
 - git commit -m "Travis CI Site updated $COMMIT"
 - git push -f origin master:"$DEPLOY_BRANCH"
+
 env:
   global:
   - DEPLOY_BRANCH: pages
   # - DEPLOY_BRANCH: legacy-pages
   - REPO: git@github.com:yeasy/docker_practice.git
+
 addons:
   ssh_known_hosts:
   - github.com
+
 branches:
   only:
   - master