Jay/make web3 store file

[JhChoy]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/HAECHI-LABS/vvisp/blob/master/CONTRIBUTING.md#commit
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)
• PR to dev branch

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Documentation content changes
• Other... Please describe:

What is the current behavior?

vvisp-utils/getWeb3 use dotenv

What is the new behavior?

• getWeb3 => web3Store
• Remove dependency of dotenv
  web3Store has 3 functions

1. setWithProvider: set web3 with provider
2. setWithURL: set web3 with http url
3. get: getter of stored web3, if there isn't, return void web3
4. delete: delete stored web3 for test

Does this PR introduce a breaking change?

• Yes
• No

[coveralls]

Pull Request Test Coverage Report for Build 383

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 3 unchanged lines in 2 files lost coverage.
• Overall coverage decreased (-24.6%) to 62.485%

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Files with Coverage Reduction	New Missed Lines	%
src/sendTx.js	1	91.18%
src/getPrivateKey.js	2	84.62%

Totals
Change from base Build 368:	-24.6%
Covered Lines:	385
Relevant Lines:	595

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💛 - Coveralls

[JhChoy]

duplicated with #101