add ripgrep to travis ci cache directories list

CI often fails for github api rate limit when downloading
ripgrep package. This workaroud is trying to enable
Travis CI cache of ripgrep package.

Signed-off-by: tom-shan <swt0008411@163.com>

.travis.yml

@@ -66,6 +66,7 @@ cache:
 # end_cache_directories
   - packages/java-debug/download
   - packages/debug-nodejs/download
+  - /tmp/vscode-ripgrep-cache-1.2.4
 branches:
   only:
   - master
@@ -87,6 +88,9 @@ addons:
     - libxkbfile-dev
     chrome: stable
 before_install:
+  - ls -l /tmp/vscode-ripgrep-cache-1.2.4
+  - ls -l node_modules
+  - ls -l /home/travis/build/theia-ide/theia/node_modules
   - |
     if [ "$TRAVIS_OS_NAME" == "linux" ]; then
       export DISPLAY=:99.0