* Update docs for older appservice bridges to enable legacy authorization

* Update docs/configuring-playbook-bridge-appservice-discord.md

Co-authored-by: Slavi Pantaleev <slavi@devture.com>

* Update docs/configuring-playbook-bridge-appservice-webhooks.md

Co-authored-by: Slavi Pantaleev <slavi@devture.com>

* further fix formatting

---------

Co-authored-by: blotree <teruyo@touhou-project.com>
Co-authored-by: Slavi Pantaleev <slavi@devture.com>

with deprecation notice

fixes HTTP 400 Error: "{\"errcode\":\"M_MISSING_PARAM\",\"error\":\"Missing key 'avatar_url'\"}"

Added steps to configure appservice webhooks in the dimension manager.

Related to #339 (Github Pull Request).