feat: Adds iconify icons to mermaid

[aanzolaavila]

Description

Adds support for iconify icons in mermaid.

This is my first PR to this repo, so any suggestion, improvements and such is deeply appreciated. I wrote this a long time ago to get these icons in my mermaid posts so probably would need adjustments to how the maintainer would do it.

Example:

{{< mermaid >}}
---
title: Example Athena Architecture
---
architecture-beta
  group vpc(logos:aws-vpc)[VPC]
  group psubnet[Private Subnet] in vpc

  service athena(logos:aws-athena)[Athena] in vpc
  service server(server)[Server] in vpc
  service storage(logos:aws-s3)[Storage] in vpc
  service database(logos:aws-rds)[RDS Postgres] in psubnet
  service dbconnector(logos:aws-lambda)[Postgres Athena connector] in psubnet
  service externalconnector(logos-aws-lambda)[Custom Athena connector] in vpc

  athena:R -- L:dbconnector

{{< /mermaid >}}

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