Update README.md

[MagicFab]

Added compatibility section and Debian 10 info

[ishikawa999]

@MagicFab

Thank you for sharing the results of the operation test.

I thought it would be better not to merge this pull request for the following reasons:
In this Redmine theme, the corresponding Redmine version is different for each branch. Install section
For example, the code in the master branch is not compatible with 4.0.3-stable.
People who see the "Compatibility section" you've added may mistakenly think that the master branch is compatible with 4.0.3-stable.

Also, Debian information is probably unnecessary as the theme is OS independent.

[MagicFab]

I think it's still valuable to save time to others. The instructions are clear which branch to clone when using different versions, that
s why I included the specific Debian version too. Redmine is not packaged yet in the current Debian stable version (11) so the Debian version was important too.

In the end the point is your theme has specific support for a full stable Debian + Redmine (cleanly packaged and supported), which I haven't seen elsewhere.

[MagicFab]

Many thanks for providing specific versions for older Redmine versions :) If there is a way to donate or support this theme otherwise I would love to do that.

[ishikawa999]

@MagicFab
Thank you for your response.

I think it's still valuable to save time to others.

I'm sure you're right.
The Redmine version corresponding to the install section is listed, but it seems kinder to have the Compatibility section as well.

I'll try to merge this pull request and add further explanation for other versions.
Example:

I have confirmed that the theme works in the next version.(As of 2021/8/31)

* Redmine3.4.x and 3.4 branch theme for this repository
* Redmine4.0.x and 4.0 branch theme for this repository

I can't work now, so I'll do it later.

s why I included the specific Debian version too. Redmine is not packaged yet in the current Debian stable version (11) so the Debian version was important too.

Yes, it is useful information that Redmine 4.0 runs on Debian.
However, I don't think this information is necessary to run this theme.
In general, installing a theme is something you think about after you have installed Redmine, and you don't read the README of a theme when you think about whether Redmine can be used on your OS.
If you want to know how to run Redmine, you should read the README of Redmine itself, its documentation, or your own personal articles describing the installation procedure of Redmine.