[bug] - If page is called with suffix (e.g. /page.html/suffix) it result in wrong URL for model.json

[marcinczeczko]

Describe the bug
Calling the page with the suffix /content/site/page.html/suffix result in a wrong URL for model.json for that page that looks like /content/site/page.model.jsonsuffix

Looking at the code it seems that the PathUtil._replaceExtension misses first /
See here:

aem-spa-page-model-manager/src/PathUtils.ts

Line 291 in 3b040b7

path += slingElementsWithoutResource.join('/');

Looks like the line 291 should be
path += '/' + slingElementsWithoutResource.join('/');

Package version
1.4.0, but issue is present in the master too

To Reproduce
Steps to reproduce the behavior:

1. Go to '...'
2. Click on '....'
3. Scroll down to '....'
4. See error

Expected behavior
Calling the page with the suffix /content/site/page.html/suffix should call for model.json with a proper URL which is /content/site/page.mode.json/suffix

Screenshots
N/A

Additional context
N/A