Update apache.md

[undersound]

On a default apache install on ubuntu 18.04 I had to enable the headers module or else I would receive the following error:

Invalid command 'RequestHeader', perhaps misspelled or defined by a module not included in the

Guidelines for Contributing

Airsonic development is a community project, and contributions are welcomed. Here are a few guidelines you should follow before submitting:

1. Styling The documentation follows some styling guidelines to fit with the website.

   • Follow the markdown guidelines. For more details see this guide.
   • Do not use <h1> or <h2> headers ( # h1 or ## h2 headers).
   • Never manually start a new line in the middle of a sentence.
   • More spacing, more empty lines !! The documentation needs to be readable !
   • Read existing guides to find some inspiration.

2. Testing The documentation is browsed with the website, so we recommend to test any new guides within the website using jekyll locally.

   • Clone the website repo git clone https://github.com/airsonic/airsonic.github.io.
   • Change directory into the cloned repo cd airsonic.github.io.
   • Clone the documentation submodule git clone https://github.com/airsonic/documentation pages/docs.
   • Install Jekyll
   • Run jekyll serve --watch.
   • Add your changes.
   • Check if everything is fine at localhost:4040.

3. License Acceptance All contributions must be licensed under GNU GPLv3 to be accepted. Use git commit --signoff to acknowledge this.

4. Be bold! Without contributions, this project will vanish.

5. Stay relevant Issues or commentary that is off-topic or tangential to Airsonic development is subject to moderation. Questions should be focused on improving documentation to solve a problem. Visit Reddit or IRC for community discussion.