Add links to the web firmware installer (#26)

* Update README.md

Add link to firmware installer

* Update step-by-step.md

add installer link

README.md

@@ -90,6 +90,10 @@ There are now 2 new PCB designs, one for SMD components and another one solely u
 [![PlatformIO CI](https://github.com/oseiler2/CO2Monitor/actions/workflows/pre-release.yml/badge.svg)](https://github.com/oseiler2/CO2Monitor/actions/workflows/pre-release.yml)
 [![Release](https://github.com/oseiler2/CO2Monitor/actions/workflows/tagged-release.yml/badge.svg)](https://github.com/oseiler2/CO2Monitor/actions/workflows/tagged-release.yml)
 
+## Installation
+
+You can install the firmware with a USB connection and your web browser via the tool at https://oseiler2.github.io/CO2Monitor/
+
 ## Wifi
 
 Supports [ESPAsync WiFiManager](https://github.com/khoih-prog/ESPAsync_WiFiManager) to set up wireless credentials and further configuration.

pcb/CO2 Monitor V0.5 through-hole/step-by-step.md

@@ -70,8 +70,7 @@ Solder the SCD30 sensor to the main PCB while making sure it lies flat on the bo
 
 ![](./17-liquid-tape.jpg)
 
-9. Before plugging the monitor in, have a good look at all components and make sure that all components are installed in the correct location and orientation, all solder joints are well done and not short circuited and everything looks right. Then plug a micro-USB cable into the ESP32 and flash the firmware.
-   The monitor will start up and display the name of its WiFi access point in the first row on the display. After a short while it will also show a CO2 reading. Don't worry that the LEDs don't turn on quite yet as they'll need to be enabled in the configuration first.
+9. Before plugging the monitor in, have a good look at all components and make sure that all components are installed in the correct location and orientation, all solder joints are well done and not short circuited and everything looks right. Then plug a micro-USB cable into the ESP32 and flash the firmware using the web interface at https://oseiler2.github.io/CO2Monitor/. The monitor will start up and display the name of its WiFi access point in the first row on the display. After a short while it will also show a CO2 reading. Don't worry that the LEDs don't turn on quite yet as they'll need to be enabled in the configuration first.
 
 ![](./18-flash.jpg)