Merge 'Document typical code flow with charts' from Kacper Madej

I'd love to contribute to Limbo, but wrapping my head around the whole
project is hard.
I decided to start by creating a diagram of a typical flow so that other
potential contributors might have an easier time :)
LMK if this is useful, I can create more of those when I dig deeper.

Closes #456

docs/internals/typical_query.md

@@ -0,0 +1,37 @@
+The following sequence diagram shows the typical flow of a query from the CLI to the [VDBE](https://www.sqlite.org/opcode.html).
+
+```mermaid
+sequenceDiagram
+
+participant main as cli/main
+participant Database as core/lib/Database
+participant Connection as core/lib/Connection
+participant Parser as sql/mod/Parser
+participant translate as translate/mod
+participant Statement as core/lib/Statement
+participant Program as vdbe/mod/Program
+
+main->>Database: open_file
+Database->>main: Connection
+main->>Connection: query(sql)
+Note left of Parser: Parser uses vendored sqlite3-parser
+Connection->>Parser: next()
+Note left of Parser: Passes the SQL query to Parser
+
+Parser->>Connection: Cmd::Stmt (ast/mod.rs)
+
+Note right of translate: Translates SQL statement into bytecode
+Connection->>translate:translate(stmt)
+
+translate->>Connection: Program 
+
+Connection->>main: Ok(Some(Rows { Statement }))
+
+note right of main: a Statement with <br />a reference to Program is returned
+
+main->>Statement: step()
+Statement->>Program: step()
+Note left of Program: Program executes bytecode instructions<br />See https://www.sqlite.org/opcode.html
+Program->>Statement: StepResult
+Statement->>main: StepResult
+```