Add basic setup for new webapp using modern web development stacks

[ikhoon]

Motivation:

This PR contains a minimal setup for new Central Domga admin page. Typescript, Webpack, React and https://chakra-ui.com/ is experimentally chosen as the build tools and the front-end framework.

Some settings could be while prototyping some pages in the following PRs. Because I still don't know which framework could be suitable for Central Dogma. Please feel free to comment on other frameworks or tools if you want to recommend them.

Modifications:

• Add webapp module and nodejs to build.gradle
• Configure webpack and add dependencies to package.json
• Implement hello world page using Chakra UI

Result:

Start the first step for the new webapp journey.

[codecov[bot]]

Codecov Report

Base: 70.42% // Head: 70.47% // Increases project coverage by +0.05% :tada:

Coverage data is based on head (9b2cd4a) compared to base (488de50). Patch has no changes to coverable lines.

:exclamation: Current head 9b2cd4a differs from pull request most recent head ce50352. Consider uploading reports for the commit ce50352 to get more accurate results

Additional details and impacted files

@@               Coverage Diff                @@
##             new-webapp     #722      +/-   ##
================================================
+ Coverage         70.42%   70.47%   +0.05%     
- Complexity         3422     3425       +3     
================================================
  Files               349      349              
  Lines             13474    13474              
  Branches           1454     1454              
================================================
+ Hits               9489     9496       +7     
+ Misses             3125     3120       -5     
+ Partials            860      858       -2     

Impacted Files	Coverage Δ
.../com/linecorp/centraldogma/client/FileWatcher.java	80.00% <0.00%> (-10.00%)	:arrow_down:
...raldogma/server/internal/api/ContentServiceV1.java	85.82% <0.00%> (+0.74%)	:arrow_up:
...internal/storage/DirectoryBasedStorageManager.java	65.06% <0.00%> (+0.87%)	:arrow_up:
.../linecorp/centraldogma/client/AbstractWatcher.java	88.66% <0.00%> (+1.33%)	:arrow_up:
...centraldogma/server/internal/api/WatchService.java	79.66% <0.00%> (+6.77%)	:arrow_up:

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