Substitution key hint shows even when a sub is used

[colleenmcginnis]

Describe the bug

I'm seeing hints suggesting that a substitution key is not used when it is used in one or more Markdown files.

Note: In the example I provided below, the Markdown file where the variables are used also use page-level subs in the frontmatter. I'm not sure if that could be the cause.

Expected behavior

I should only get hints when a substitution key is actually not used.

Steps to reproduce

Here's an example:

1. The build for apm-agent-nodejs shows two hints:

   Hint: Substitution key 'ecloud' is not used in any file
   NOTE: /github/workspace/docs/docset.yml
    
   Hint: Substitution key 'apm-lambda-ext' is not used in any file
   NOTE: /github/workspace/docs/docset.yml
   

2. But when I check for usage of those subs, I find uses:
   • {{ecloud}}: https://github.com/elastic/apm-agent-nodejs/blob/main/docs/reference/lambda.md?plain=1#L21
   • {{apm-lambda-ext}}: https://github.com/elastic/apm-agent-nodejs/blob/main/docs/reference/lambda.md?plain=1#L25

Tooling

• docs-builder
• migration tooling
• I'm not sure

[colleenmcginnis]

This seems to be pretty widespread in recent PRs.

[shainaraskas]

Note: In the example I provided below, the Markdown file where the variables are used also use page-level subs in the frontmatter. I'm not sure if that could be the cause.

I'm seeing this in pages where there are no front matter keys set

[Mpdreamz]

Forgot one line in the one place we parse variables 😸

#809 should fix this.

[colleenmcginnis]

Thank you! I'm still seeing a few problems 😬 #814.