Write reference "Linux Filesystem Hierarchy Standard"

[dviererbe]

(Canonical internal) JIRA link: https://warthogs.atlassian.net/browse/FR-4938

User story

As a new Ubuntu/Linux developer, when I am looking for where to install the built files of my package, I want to have a concise reference so that I can easily understand the Linux Filesystem Hierarchy Standard (FHS).

Context

Ubuntu adheres to the Linux Filesystem Hierarchy Standard (FHS). A small introductory reference – covering the most common locations – could help new developers grasp the concepts more easily. This reference does not need to feature the complete FHS, but rather the most important/common locations and refer to the FHS for special cases.

Acceptance Criteria

• Create a small introductory reference for the FHS.
• Provide an overview that is easily consumable by new developers.
• Ensure the reference aligns with the latest FHS 3 specification.