feat(init-generator): add svelte template

[jamesgeorge007]

What kind of change does this PR introduce?
feature

Did you add tests for your changes?
Yes

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

Summary
This PR aims at adding a svelte template for init-generator #2832

Does this PR introduce a breaking change?
No

Other information
N/A

[codecov]

Codecov Report

Merging #2859 (22ee992) into master (d9d4c37) will decrease coverage by 0.29%.
The diff coverage is 73.91%.

@@            Coverage Diff             @@
##           master    #2859      +/-   ##
==========================================
- Coverage   95.01%   94.71%   -0.30%     
==========================================
  Files          31       32       +1     
  Lines        1706     1723      +17     
  Branches      498      497       -1     
==========================================
+ Hits         1621     1632      +11     
- Misses         85       91       +6     

Impacted Files	Coverage Δ
packages/generators/src/utils/helpers.ts	74.07% <42.85%> (-10.93%)	⬇️
packages/generators/src/handlers/svelte.ts	85.71% <85.71%> (ø)
packages/generators/src/addon-generator.ts	91.83% <100.00%> (-0.76%)	⬇️
packages/generators/src/handlers.ts	100.00% <100.00%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 9b326f6...22ee992. Read the comment docs.

[rishabh3112]

We should also add support for postcss, sass, etc here. Like we have in default template. Maybe we can have some refactoring here.

[alexander-akait]

I agree, ideally we should extend default template and add custom loaders/plugins

[evenstensberg]

We don’t need this. CWA (create webpack app) is going to be a standalone tool soon. Gsoc project.