tests(generate-plugin): add test case for scaffolding in the current directory

[jamesgeorge007]

What kind of change does this PR introduce?
tests

Did you add tests for your changes?
Yes

If relevant, did you update the documentation?
N/A

Summary
Follow up of #2073

Does this PR introduce a breaking change?
Nope

Other information
N/A

[codecov]

Codecov Report

Merging #2082 (d7033b9) into master (7d97efe) will increase coverage by 0.04%.
The diff coverage is 92.30%.

@@            Coverage Diff             @@
##           master    #2082      +/-   ##
==========================================
+ Coverage   68.45%   68.50%   +0.04%     
==========================================
  Files          76       76              
  Lines        2400     2413      +13     
  Branches      495      497       +2     
==========================================
+ Hits         1643     1653      +10     
- Misses        757      760       +3     

Impacted Files	Coverage Δ
packages/serve/src/startDevServer.ts	85.71% <66.66%> (-5.60%)	⬇️
packages/generate-plugin/src/index.ts	100.00% <100.00%> (ø)
packages/generators/src/init-generator.ts	94.00% <100.00%> (+0.06%)	⬆️
packages/init/src/index.ts	100.00% <100.00%> (ø)
packages/utils/src/modify-config-helper.ts	54.09% <100.00%> (-0.91%)	⬇️
packages/utils/src/scaffold.ts	76.00% <100.00%> (ø)
packages/webpack-cli/lib/utils/package-exists.js	83.33% <100.00%> (ø)

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[alexander-akait]

Weird, coverage is reduced

[snitin315]

It's increased now.