AddOutputFilterByType has been moved from mod_deflate to mod_filter in Apache 2.3.7. Without the mod_filter module loaded Apache will error out reading the p/.htaccess file.

Apache documentation about the AddOutputFilterByType directive for reference:
https://httpd.apache.org/docs/2.4/mod/mod_filter.html#addoutputfilterbytype

This issue was encountered when installing FreshRSS 1.26.0 in a shared hosting environment where compression is applied at the reverse proxy, not the Apache web server.

Changes proposed in this pull request:

Add check in .htaccess for Apache mod_filter to ensure AddOutputFilterByType works.

It may also be necessary to update the Apache LoadModule configuration to include mod_filter for the Docker container files. I haven't tested running this with Docker.

How to test the feature manually:

1. Setup Apache 2.4 with mod_deflate, but without mod_filter loaded.
2. Install FreshRSS 1.26.0 and try to run it.
3. Notice it doesn't work and the Apache error logs complains about missing the module for AddOutputFilterByType
4. Apply this patched .htaccess and try again, notice that it now works as Apache knows to ignore the AddOutputFilterByType directive due to missing mod_filter. If both mod_filter and mod_deflate are loaded it will also work.

Pull request checklist:

• clear commit messages
• code manually tested
• unit tests written (optional if too hard)
• documentation updated