Installation description in README doesn't have a lot of small details

[krllstdn]

• libssl1.1.1. for wkhtmltopdf
• npm and node should be of a newer versions. otherwise some packages will not work. (by default apt installs version of node 12 which is too old for some packages)
• swagger (openapi-generator) needs java 8 to work Swagger generation needs Java 8  #1091
• sudo npm install -g @openapitools/openapi-generator-cli in frontend readme
• first launch on Ubuntu system must be with super user rights (sudo openapi-generator-cli validate -i txmatching/web/swagger/swagger.yaml - command from Makefile). After that we can use regular make validate-swagger command. We need that to install the last version of openapi-generator (first run on the system makes an update because the version of it in npm is too old)

All described above is related to Ubuntu system and Ubuntu-based WSL

[krllstdn]

was blocked by #1091