feat: add 4 new blogs (PG18 mirror, Oracle De-O, Cgroup, FDW) - #266

Changed pages include:

• index.html - view
• 404.html - view
• blog/index.html - view
• community-page/index.html - view
• contribution-guidelines/index.html - view
• contributors/index.html - view
• customer-stories-page/index.html - view
• docs-ecosystem/index.html - view
• docs-installation/index.html - view
• download-page/index.html - view

There are more changes not included in the list