For the ReadMe file:

the listed Firefox add-on node exists no longer, two current similar add-ons located:
SQLite Manager at https://addons.mozilla.org/en-US/firefox/addon/sqlite-manager-webext/
SQLite Reader at https://addons.mozilla.org/en-US/firefox/addon/sql-reader/

SQLiteStudio still going strong as listed, v3.2.1 2018-07-27
extensible at GitHub https://github.com/pawelsalawa/sqlitestudio/wiki/Official_plugins

Github https://github.com/search?q=sqlite

Link to http://www.dbsoftlab.com/database-editors/database-browser/overview.html now redirects to website https://www.etl-tools.com/
and their free tool https://www.etl-tools.com/database-browser/overview.html