Bug/fix help images not loading on paths with spaces

Prerequisites

[x] Reviewed the checklist
[x] Reviewed feedback from the "Sonar Cloud" bot. Note that you have to wait for the "CI / Unit Tests") to complete first. Failed Unit tests can be debugged by adding the label "verbose logging" to the GitHub PR.

Description of the Change

Small fix when handling request to replace encoded spaces in file paths with actual spaces. Also renamed all .PNG files to .png. Which was causing images to not load on linux help pages.

Alternate Designs

N/A

Why Should This Be In Core?

N/A

Benefits

Images will now display, even if there is a space in the filepath.

Possible Drawbacks

None.

Verification Process

Build consty into an application, if you are not using a consty application already.
Move the whole consty application into a folder that has spaces in its name. If required, create on yourself.
Start consty
Open any help page
Observe images load correctly

To verify issue exists on older versions, repeat the steps above with an older version and observe images not loading on any help page.

Applicable Issues

https://github.com/constellation-app/constellation/issues/2135

constellation-app / constellation

Bug/fix help images not loading on paths with spaces #2155