fix: uri encode usage inside getReadme

[safonovklim]

🚨 Proposed changes

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[[Describe the big picture of your changes here to communicate to the maintainers why we should accept this pull request. If it fixes a bug or resolves a feature request, be sure to link to that issue.]]

⚙️ Types of changes

• Change URI encoding function to support relative paths

What types of changes does your code introduce? Put an x in the boxes that apply

• New feature (non-breaking change which adds functionality)
• Bugfix (non-breaking change which fixes an issue)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Update (if none of the other choices apply)
• Refactor

Additional context

Hello world,

First of all, thank you for a great plugin!

I noticed unexpected behavior of the README.md component. I have a monorepo where each folder is a standalone component (terraform module in my case). I was able to successfully import modules to Backstage using Location (on the root level) and Component (spec type=library inside each folder)

# root level:
README.md
catalog-info.yml

module-a/
module-a/README.md
module-a/catalog-info.yml

module-b/
module-b/README.md
module-b/catalog-info.yml

As you can see, every module has its own README, and I was trying to pass the readme annotation:

gitlab.com/readme-path: module-a/README.md

This annotation was translated to following url:

curl 'https://<my-backstage-instance-domain>/api/gitlab/gitlab.com/projects/<GITLAB_PROJECT_ID>/repository/files/module-a/README.md/raw?ref=develop'

and this request failed with 404. Upon checking Gitlab docs

https://docs.gitlab.com/ee/api/repository_files.html

I noticed that path must be URL encoded and correct URL would be like this:

curl 'https://<my-backstage-instance-domain>/api/gitlab/gitlab.com/projects/<GITLAB_PROJECT_ID>/repository/files/module-a%2FREADME.md/raw?ref=develop'

(/ -> %2F)

However, it's not happening in the current plugin version.

When I tried to replace the annotation path with already encoded version, it was encoded again

gitlab.com/readme-path: module-a%2FREADME.md

resulting in the following cURL request:

curl 'https:///<my-backstage-instance-domain>/api/gitlab/gitlab.com/projects/<GITLAB_PROJECT_ID>/repository/files/module-a%252FREADME.md/raw?ref=main' 

Either approaches don't work correctly.

More context https://stackoverflow.com/questions/4540753/should-i-use-encodeuri-or-encodeuricomponent-for-encoding-urls

That said, I believe encodeURIComponent will serve the purpose and allow correct relative paths

That's it!
Thank you <3