docs(readme): add 3X-UI Manager to Community Tools (#6266)
* docs(readme): add 3X-UI Manager to Community Tools
* docs(readme): add the Community Tools entry to the localized READMEs
The section is mirrored in all seven READMEs, and #4114 added it to every one
of them in a single commit — adding the entry to the English file alone leaves
the other six readers with a silently shorter list.
Each line uses that file's own wording for "License" and for
inbounds/clients/nodes, matching the entry above it.