Authors.md file already exists

[CaidenKehrer]

Some Extensions replace the authors.md file, This causes a crash when attempting to add the extension.

Example:
https://download.osgeo.org/postgis/windows/pg96/postgis-bundle-pg96-3.2.3x64.zip
This zip file creates the authors.md file. However, since it already exists from psql it causes an exception.

[mysticmind]

Thanks for reporting this, will address it in the upcoming release 2.0.0

[mysticmind]

2.0.0 released with a fix for this issue.