fix: open option for CLI without arguments

[alexander-akait]

• This is a bugfix
• This is a feature
• This is a code refactor
• This is a test update
• This is a docs update
• This is a metadata update

For Bugs and Features; did you add new tests?

No, but tests will be added on webpack-cli side

Motivation / Use-Case

fixes webpack/webpack-cli#2001

Breaking Changes

No

Additional Info

No

[codecov]

Codecov Report

Merging #2948 (0af6d9a) into v3 (4ab1f21) will increase coverage by 0.95%.
The diff coverage is n/a.

@@ Coverage Diff @@ ## v3 #2948 +/- ## ========================================== + Coverage 93.77% 94.72% +0.95%  ========================================== Files 34 41 +7 Lines 1333 1915 +582 Branches 381 593 +212 ========================================== + Hits 1250 1814 +564  - Misses 81 98 +17  - Partials 2 3 +1 

Impacted Files	Coverage Δ
lib/utils/setupExitSignals.js	94.44% <0.00%> (-5.56%)	⬇️
lib/utils/updateCompiler.js	97.36% <0.00%> (-2.64%)	⬇️
lib/Server.js	96.58% <0.00%> (-0.21%)	⬇️
lib/utils/createDomain.js	100.00% <0.00%> (ø)
lib/utils/normalizeOptions.js	100.00% <0.00%> (ø)
client-src/default/utils/log.js	100.00% <0.00%> (ø)
client-src/default/utils/createSocketUrl.js	100.00% <0.00%> (ø)
lib/utils/DevServerPlugin.js	100.00% <0.00%> (ø)
client-src/transpiled-modules/strip-ansi.js	100.00% <0.00%> (ø)
lib/utils/getColorsOption.js	100.00% <0.00%> (ø)
... and 14 more

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[alexander-akait]

Let's merge and do patch release, I will fix CI (for azure) for v3 if we need more patch releases