Clarify external packages must have source code published (#2172)

* Clarify external packages must have source code published

* Improve language

* Improve language

* Update docs/api_lib_index.md

Co-authored-by: Joost Lekkerkerker <joostlek@outlook.com>

* Update docs/creating_component_code_review.md

* Update docs/api_lib_index.md

* Update docs/api_lib_index.md

---------

Co-authored-by: Joost Lekkerkerker <joostlek@outlook.com>

docs/creating_component_code_review.md

@@ -15,11 +15,11 @@ Not all existing code follows the requirements in this checklist. This cannot be
  2. Use existing constants from [`const.py`](https://github.com/home-assistant/core/blob/dev/homeassistant/const.py)
     - Only add new constants to `const.py` if they are widely used. Otherwise keep them on components level
 
-### 1. Requirements
+### 1. External requirements
 
  1. Requirements have been added to [`manifest.json`](creating_integration_manifest.md). The `REQUIREMENTS` constant is deprecated.
- 2. Requirement version should be pinned: `"requirements": ['phue==0.8.1']`
- 3. We no longer want requirements hosted on GitHub. Please upload to PyPi.
+ 2. Requirement version must be pinned: `"requirements": ['phue==0.8.1']`
+ 4. Each requirement meets the [library requirements](api_lib_index.md#basic-library-requirements).
 
 ### 2. Configuration