ui: add a welcome page when no any test suites

[LinuxSuRen]

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[codacy-production]

Coverage summary from Codacy

See diff coverage on Codacy

Coverage variation	Diff coverage
-0.11%	∅

Coverage variation details

	Coverable lines	Covered lines	Coverage
Common ancestor commit (4e464d1)	5230	4457	85.22%
Head commit (19f3134)	5230 (+0)	4451 (-6)	85.11% (-0.11%)

Coverage variation is the difference between the coverage for the head and common ancestor commits of the pull request branch: <coverage of head commit> - <coverage of common ancestor commit>

Diff coverage details

	Coverable lines	Covered lines	Diff coverage
Pull request (#184)	0	0	∅ (not applicable)

Diff coverage is the percentage of lines that are covered by tests out of the coverable lines that the pull request added or modified: <covered lines added or modified>/<coverable lines added or modified> * 100%

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[sonarcloud]

SonarCloud Quality Gate failed.   

2 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
0.0% Duplication

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[github-actions]

There are 17 test cases:

API	Average	Max	Min	Count	Error
POST http://localhost:8080/server.Runner/FunctionsQuery	2.694671ms	2.694671ms	2.694671ms	1	0
POST http://localhost:8080/server.Runner/GetSuites	2.314247ms	2.314247ms	2.314247ms	1	0
POST http://localhost:8080/server.Runner/GetStores	2.264844ms	2.264844ms	2.264844ms	1	0
POST http://localhost:8080/server.Runner/UpdateTestSuite	2.193139ms	2.193139ms	2.193139ms	1	1
POST http://localhost:8080/server.Runner/CreateTestSuite	1.25038ms	1.25038ms	1.25038ms	1	0
POST http://localhost:8080/server.Runner/GetTestCase	1.083569ms	1.083569ms	1.083569ms	1	0
POST http://localhost:8080/server.Runner/GetSecrets	876.555µs	876.555µs	876.555µs	1	0
POST http://localhost:8080/server.Runner/GetTestSuite	808.351µs	808.351µs	808.351µs	1	0
POST http://localhost:8080/server.Runner/ListTestCase	794.35µs	1.147873ms	440.828µs	2	1
POST http://localhost:8080/server.Runner/ListConverter	760.349µs	760.349µs	760.349µs	1	0
POST http://localhost:8080/server.Runner/GetSuggestedAPIs	729.346µs	729.346µs	729.346µs	1	0
POST http://localhost:8080/server.Runner/PopularHeaders	633.04µs	633.04µs	633.04µs	1	0
POST http://localhost:8080/server.Runner/DeleteTestSuite	588.587µs	760.849µs	416.326µs	2	1
POST http://localhost:8080/server.Runner/ListCodeGenerator	581.537µs	581.537µs	581.537µs	1	0
POST http://localhost:8080/server.Runner/GetVersion	562.936µs	562.936µs	562.936µs	1	0
POST http://localhost:8080/server.Runner/GenerateCode	502.832µs	502.832µs	502.832µs	1	1
POST http://localhost:8080/server.Runner/ConvertTestSuite	465.73µs	465.73µs	465.73µs	1	1