feat(oidc-auth): support empty OIDC client secret

[tarasglek]

Hi,
I found that this library does not work with https://lastlogin.net/developers/

Would a change like this be ok?

[changeset-bot]

🦋 Changeset detected

Latest commit: 215f376

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@hono/oidc-auth	Minor

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[yusukebe]

@tarasglek

Can you run yarn changeset on the top of the project and push the generated file?

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 66.66667% with 1 line in your changes missing coverage. Please review.

Project coverage is 79.50%. Comparing base (6c36f52) to head (215f376).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
packages/oidc-auth/src/index.ts	66.66%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1126      +/-   ##
==========================================
- Coverage   79.53%   79.50%   -0.03%     
==========================================
  Files          77       77              
  Lines        2282     2284       +2     
  Branches      578      580       +2     
==========================================
+ Hits         1815     1816       +1     
- Misses        391      392       +1     
  Partials       76       76              

Flag	Coverage Δ
oidc-auth	9.98% <66.66%> (-0.02%)	⬇️

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[yusukebe]

Hi @hnw! Can you review this? We should add tests, but if it's difficult, it's okay not to.

[tarasglek]

I ran yarn changeset, hope I did this right

[tarasglek]

all good now?

[tarasglek]

ping to get this landed

[yusukebe]

@tarasglek

Can you write a proper test?