use relative paths for assets to run not in docroot

[dklimpel]

Bring back, that the index.html load asstes with relative paths that using in root path ist not required.

src=/assets/ -> src=./assets/

Fixes:

• 517

• 519

Related to:

• 11

• https://github.com/Awesome-Technologies/synapse-admin/commit/1002b6464a1093b000ebf1d3e9b26cb04526ff11