Add some notes about sysadmin skills when installing LWC

[Gustry]

When installing Lizmap, there are a few things which are not explained in the documentation :

• to know how to set environment variables (QGIS server for instance)
• restart and manage processes and read their respective logs stderr
• understand differences between QGIS server installation : apache, nginx, systemd, supervisor etc

[Gustry]

Using CURL to debug HTTP requests to QGIS server

[3liz-bot]

The backport to lizmap_3_5 failed:

The process '/usr/bin/git' failed with exit code 1

stderr

``` error: could not apply 9f13e4a... Add some notes about sysadmin skills when installing LWC hint: After resolving the conflicts, mark them with hint: "git add/rm ", then run hint: "git cherry-pick --continue". hint: You can instead skip this commit with "git cherry-pick --skip". hint: To abort and get back to the state before "git cherry-pick", hint: run "git cherry-pick --abort". ```

stdout

``` Auto-merging source/install/pre_requirements.rst CONFLICT (content): Merge conflict in source/install/pre_requirements.rst ```

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add .worktrees/backport-lizmap_3_5 lizmap_3_5
# Navigate to the new working tree
cd .worktrees/backport-lizmap_3_5
# Create a new branch
git switch --create backport-221-to-lizmap_3_5
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick 9f13e4aadcb8e80dd0ef75db7198644a87551352
# Push it to GitHub
git push --set-upstream origin backport-221-to-lizmap_3_5
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-lizmap_3_5

Then, create a pull request where the base branch is lizmap_3_5 and the compare/head branch is backport-221-to-lizmap_3_5.