Create a `json-server` based fake API

[sultan-duisenbay]

Major changes

• Fake API spits out the data defined in fake-api/data.json with the routes configured in fake-api/routes.json
• Created separate web-dev-server configs (1 using fake API, 1 for prod API)
• Changed the web-test-runner config to use fake API (this should prevent flakes in the other PRs)
• Added the npm run start commands for local and k8s to visualize different data
• Updated README

[google-oss-prow[bot]]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: sultan-duisenbay

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Needs approval from an approver in each of these files: - ~~[OWNERS](https://github.com/GoogleCloudPlatform/testgrid/blob/master/OWNERS)~~ [sultan-duisenbay] Approvers can indicate their approval by writing `/approve` in a comment Approvers can cancel approval by writing `/approve cancel` in a comment

[google-oss-prow[bot]]

@sultan-duisenbay: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
test-testgrid-npm	b2a81b0ba015a7c094719d1c35c9d61c58a0d299	link	true	/test test-testgrid-npm

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[sultan-duisenbay]

Created a new PR for this stuff.