added wiki docs

docs/Building-firmware.md

@@ -0,0 +1,60 @@
+### Using the PlatformIO IDE
+
+- Download [Git](https://git-scm.com/download/win) (install using the default settings)
+- Download and install [Visual Studio Code](https://code.visualstudio.com/docs/?dv=win) (VSC)
+- Restart the PC (if using Windows) to apply the new PATH settings. It should now detect Git
+- Install the VSC extension "PlatformIO IDE"
+- Git clone this repo with "git clone" from the command palette and using the URL https://github.com/proddy/EMS-ESP.git
+- Install NodeJS from [here](https://nodejs.org/en/download/).
+- Test if Node is installed correctly by `node --version` (both v10 and v12 are ok)
+- Install the modules in the `tools/webfilesbuilder` folder with:
+```
+cd tools/webfilesbuilder
+npm ci
+```
+- Check you can build the web files by typing `node node_modules/gulp/bin/gulp.js` from the `webfilesbuilder` folder.
+- Finally use the build targets in PlatformIO's to build & upload.
+
+If you seeing fatal errors in the npm install and came from an earlier build then you'll may need to refresh the library, like
+1. Remove the local `node_modules`
+2. Clean npm cache by `npm cache verify`
+3. Update the global npm by `sudo npm ci -g npm`
+4. Reinstall the local `node_modules` by `npm ci`
+
+### Using Linux CLI
+
+- Install python:
+```sh
+sudo apt install python-pip
+```
+- Install PlatformIO (see  https://docs.platformio.org/en/latest/installation.html):
+```sh
+python -c "$(curl -fsSL https://raw.githubusercontent.com/platformio/platformio/develop/scripts/get-platformio.py)"
+```
+- Edit `~/.profile` and add: `export PATH=$PATH:~/.platformio/penv/bin` to the end, then `exit`, and start a new shell
+- Update platformio and its libraries
+```sh
+platformio platform update
+platformio lib update
+```
+- Grab the EMS-ESP source code:
+```sh
+git clone https://github.com/proddy/EMS-ESP.git
+```
+ (use `git clone --branch=dev https://github.com/proddy/EMS-ESP.git` for dev builds)
+- Install NodeJS. See instructions [here](https://tecadmin.net/install-latest-nodejs-npm-on-ubuntu/).
+- Install the EMS-ESP's web builder components
+```sh
+cd EMS-ESP/tools/webfilesbuilder
+npm ci
+cd ../..
+```
+- Build the firmware image:
+```sh
+pio run
+```
+- Upload to firmware image. This uses OTA as default. Change `platformio.ini` if using USB
+```sh
+pio run -t upload
+```
+