Added path of the extension directory, removed some typo and Resolved the issue(#803).

Removed a small typo.

Resolved the issue `Documentation repos are not listed at docs/documentation/index.md #803` (https://github.com/civicrm/civicrm-dev-docs/issues/803).

Added path of the extension directory and removed some typo.

Improve examples of hook_civicrm_alterExternUrl

Update to reflect https://github.com/civicrm/civicrm-core/pull/16903

Update Documentation > Writing Documentation

Add clarification around <ver> tags in info.xml files.

UI Reference: document icon helper functions and screen reader text

Hooks in Symfony - Discuss the $priority option

When this was first written, I figured that `$priority` is explained in
upstream docs.  However, the truth is that they don't give any guidance on
*what numbers to use* or *how/whether to spread out the numbers*.

This describes some current examples and suggests a general formulation for
folks in doubt.

Fix link to documentation on symfony hooks in apiwrappers hook docume…

dev/core#1744 - Cleanup event naming

See also:

* dev/core#1744
* https://github.com/civicrm/civicrm-core/pull/17240