Feat (RAG): tying tui calls to rag funcs [WIP; skip-ci]

RAG itself is annoying to properly implement, plucking sentences with no
context is useless. Also it should not be a part of main package, same
for goes for tui. The number of global vars is absurd.

config.example.toml

@@ -1,4 +1,5 @@
 APIURL = "http://localhost:8080/v1/chat/completions"
+EmbedURL = "http://localhost:8080/v1/embeddings"
 ShowSys = true
 LogFile = "log.txt"
 UserRole = "user"