Add options when initializing the plugin

We need to provide a way for users to modify core functionalities of the plugin, as shown in the official docs here: https://v2.docusaurus.io/docs/using-plugins#configuring-plugins

I suggest to add options for the following configuration:

• TERMS_DIR: default value: ./docs/terms and allow the users to specify their own dir
• glossaryPath: default value: ./docs/glossary.md and allow the users to specify their own glossary path
• pattern separator: default value: |, and we should find a way to combine it with the above regex pattern, so people can choose a different one
• Add an array of files to be excluded from search/replace and to be added in glossary
• Provide the option to change styles for the popup? I'm not sure about that.

regex pattern: default value: /\%%.*?\|.*?\%%/g and allow users to modify it (we'll drop this one)