Standalone install guide updates

See merge request !69

Update PHP requirements for CiviCRM 5.75 ESR

See merge request !70

Correct drupal references in Backdrop page

See merge request !68

Update index.md to publish assets (got idea from...

See merge request !58

PHP 8.2 now recommended, removed some PHP <7.2 cruft

See merge request !67

Increase ESR version, drop PHP 7.3 for non-ESR release, update historical PHP versions

See merge request !66

Indicate that 8.2 and 8.3 are supported for certain sites

See merge request !65

Change composer requirement to civicrm/cli-tools to circumvent dependency errors

See merge request !64

Replace "composer require civicrm/cli-tools" with "composer require civicrm/cv" since the latter one produces dependency errors in the described workflow.

My environment is Debian 12 with its default apache2 (plus config for rewrite) and mariadb and php8.1 (plus the following php extensions: xml gd mysql mbstring intl zip).

I got the idea for the differen composer requirement from https://packagist.org/packages/civicrm/cv

Bump to PHP 8.3

See merge request !63

Put in caution about extensions potentially causing issues when upgrading PHP

See merge request !62

Updated to change CMS language from required to recommended for versions with security support as of 2023-11 and says it works with various earlier versions.

Updated to show Joomla 3 and 4 supported. Changed PHP 8.0 to not recommended as losing security support this month.

Drop PHP 7.2. Mark PHP 7.3 as not recommended

See merge request !61