Add redis, and specify in more details + add php7.4 mention

[seansan]

Description (*)

Related Pull Requests

Fixed Issues (if relevant)

1. Fixes Can we update all minor and advised version for redis 6? / mysql 8? / php 7.4 in readme? #1188

Manual testing scenarios (*)

1. ...
2. ...

Questions or comments

Contribution checklist (*)

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All automated tests passed successfully (all builds are green)

[Flyingmana]

technically Redis is not an requirement, but mentioning this somehow as optional, and which versions we support is something good.

Also approval for the mentioned version of Redis (have seen the chat regarding it in Discord)

[seansan]

Maybe make some small pull requests? And then approve 1 by 1 ...

On the other hand if we have some minimum amount of users/admins confirming their versions then we know a lot

In general I could imagine

Requirements

• NAME1 Minimal and Maximum advised version (e.g. PHP)
• NAME2 Minimal and Maximum advised version (e.g. Mysql)

Additional Requirements

• NAME1 Minimal and Maximum advised version (e.g. Redis)

[fballiano]

I think system requirements should be divided by branch (19 and 20 at the moment), redis should be marked as optional and I'd suggest php7.4 for openmage20 instead of php7.3

[github-actions]

Unit Test Results

1 files  ±0  1 suites  ±0   0s ⏱️ ±0s
0 tests ±0  0 ✔️ ±0  0 💤 ±0  0 ❌ ±0 
6 runs  ±0  4 ✔️ ±0  2 💤 ±0  0 ❌ ±0 

Results for commit 2b84ee1. ± Comparison against base commit 95bb164.