update readme

BUILDING.md

@@ -0,0 +1,64 @@
+## Get the source and install the requirements:
+
+```shell
+$ git clone https://github.com/seird/gotify-tray.git
+$ cd gotify-tray
+$ pip install -r requirements.txt
+```
+
+
+### Run from source
+
+```shell
+$ python -m gotify_tray
+```
+
+### Create a pyinstaller executable
+
+```shell
+$ pip install pyinstaller
+$ pyinstaller gotify-tray.spec
+```
+An executable is created at `dist/gotify-tray/`.
+
+### Create a macos .app
+
+```shell
+$ pip install pyinstaller Pillow
+$ pyinstaller gotify-tray.spec
+```
+
+### Inno setup (Windows)
+
+Create an installer for windows with inno setup from pyinstaller output:
+
+```shell
+$ iscc gotify-tray.iss
+```
+
+### Create and install a pip package
+
+- Create the pip package:
+    ```shell
+    $ python -m build
+    ```
+
+- Install the pip package:
+    ```shell
+    $ pip install dist/gotify_tray-0.1.14-py3-none-any.whl
+    ```
+
+- Launch:
+    ```shell
+    $ gotify-tray
+    ```
+
+### Create a deb package
+
+```shell
+$ make build
+
+# or install
+
+$ sudo make install
+```