chore: make intcode an installable package

- Move intcode/ from 2019/ folder to the root of the repository
- The package is automatically installed with the adventofcode package
  with `pip install -e .` command

adventofcode/intcode/README.md

@@ -0,0 +1,53 @@
+# Intcode
+
+Interpreter for the Intcode programming language used in Advent of Code 2019.
+
+## Installation
+
+The package is automatically installed with the adventofcode package:
+
+```bash
+pip install -e .
+```
+
+## Usage
+
+```python
+from adventofcode.intcode import interpret_intcode, Interpreter
+
+# Simple execution
+result = interpret_intcode([1, 0, 0, 0, 99])
+print(result.memory)  # [2, 0, 0, 0, 99]
+
+# With stdin
+result = interpret_intcode([3, 0, 99, 0], stdin=[42])
+print(result.stdout)  # [42]
+
+# For more control, use the Interpreter class
+interpreter = Interpreter([3, 9, 8, 9, 10, 9, 4, 9, 99, -1, 8])
+interpreter.stdin = [8]
+interpreter.interpret()
+print(interpreter.stdout)  # [1]
+```
+
+## API
+
+### `interpret_intcode(program, stdin=[])`
+Execute an Intcode program and return the Interpreter object.
+
+- `program`: List of integers representing the Intcode program
+- `stdin`: List of integers to use as input
+
+### `class Interpreter`
+Intcode interpreter with more control options.
+
+- `stdin`: List of integers for input
+- `stdout`: List of integers for output
+- `memory`: The program memory
+- `halted`: Boolean indicating if the program has halted
+- `interpret(break_on_input=False, break_on_output=True)`: Run the interpreter
+
+### Enums
+- `Operation`: ADDITION, MULTIPLICATION, INPUT, OUTPUT, JMP_IF_TRUE, JMP_IF_FALSE, LESS_THAN, EQUALS, BASE, TERMINATION
+- `Mode`: POSITION, IMMEDIATE, RELATIVE
+