update change 'import brainpy' to 'import brainpy.state' (#54)

* update change import brainpy to brainpy.state

* Update brainpy import to use brainpy.state for improved module structure

* Replace brainpy dependency with brainpy-state for consistency in project requirements

---------

Co-authored-by: Chaoming Wang <adaduo@outlook.com>

Author: xinzhu-L

braintrace/nn/_readout.py

@@ -23,7 +23,7 @@
 import brainunit as u
 import jax
 
-import brainpy
+import brainpy.state
 from braintrace._etrace_concepts import ETraceParam
 from braintrace._etrace_operators import MatMulOp
 from braintrace._typing import Size, ArrayLike, Spike

docs/quickstart/concepts-en.ipynb

@@ -34,7 +34,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 1,
+   "execution_count": null,
    "id": "848fc7b2e198e56f",
    "metadata": {
     "ExecuteTime": {
@@ -49,7 +49,7 @@
     "import brainunit as u\n",
     "import braintrace\n",
     "import braintools\n",
-    "import brainpy"
+    "import brainpy.state"
    ]
   },
   {

docs/quickstart/concepts-zh.ipynb

@@ -32,7 +32,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 1,
+   "execution_count": null,
    "id": "ab3ce87e1b97441d",
    "metadata": {
     "ExecuteTime": {
@@ -43,7 +43,7 @@
    },
    "outputs": [],
    "source": [
-    "import brainpy\n",
+    "import brainpy.state\n",
     "import braintools\n",
     "import brainstate\n",
     "import brainunit as u\n",