Replace 'or (||)' cond with default params

[etroynov]

Hi,

According or packages.json the minimal version of node js is 8 and it's good because since from version 6 we can use default params for function arguments:

• github
• MDN

Checklist

• I have ensured my pull request is not behind the main or master branch of the original repository.
• I have rebased all commits where necessary so that reviewing this pull request can be done without having to merge it first.
• I have written a commit message that passes commitlint linting.
• I have ensured that my code changes pass linting tests.
• I have ensured that my code changes pass unit tests.
• I have described my pull request and the reasons for code changes along with context if necessary.

[etroynov]

@3imed-jaberi @niftylettuce can you review pls. thx.

[titanism]

We have just published @koajs/router v11.0.0 which resolves this issue. This is mirrored to koa-router as well.

https://github.com/koajs/router/releases/tag/v11.0.0

This project is maintained by Forward Email and Lad.