feat: Radiomaster GX15 support (#7643)

Co-authored-by: 3djc <3djc@gh.com>
Co-authored-by: Claude Opus 5 <noreply@anthropic.com>
Co-authored-by: philmoz <phil.a.mitchell@gmail.com>
Co-authored-by: Peter Feerick <pfeerick@users.noreply.github.com>

.github/workflows/build_fw.yml

@@ -87,7 +87,8 @@ jobs:
           - tprov2;tpros;bumblebee
           - mt12;gx12;t20;t20v2
           - t12max;tx12mk2;boxer
-          - tx15;tx16s
+          - tx16s
+          - tx15;gx15
           - x12s;f16
           - v14;v14lcd;v16
           - x10;x10express

.github/workflows/companion.yml

@@ -59,7 +59,7 @@ jobs:
           - id: color-4
             target: [nb4p, st16, pa01, c14]
           - id: color-5
-            target: [t15pro, tx16smk3]
+            target: [t15pro, tx16smk3, gx15]
 
     steps:
       - name: Check out the repo

.github/workflows/nightly.yml

@@ -38,7 +38,7 @@ jobs:
           - nb4p
           - st16
           - c14
-          - tx15
+          - tx15;gx15
           - t15pro
           - v12
     container:

.github/workflows/release-drafter.yml

@@ -177,7 +177,7 @@ jobs:
             > If you are using a STM32 F2 based radio, *stop right now*, this release is not for you! EdgeTX v2.11 is the last release series to support these radios. Check [this list](https://hackmd.io/@edgetx/B12oQyQKye) if you are unsure if this affects you. Because of this, EdgeTX v2.11 will continue to be supported alongside 2.12, 3.0, etc., with a focus on bug fixes.
 
             > [!WARNING]
-            > Radios based on STM32H7 MCUs update differently to older radios. Do **not** use the "Flash via USB" option in EdgeTX Buddy with them (yet). To update radios such as the Flysky PA01 & ST16, Jumper T15 Pro, RM TX15 and RM TX16S MK3, please follow the instructions in the [EdgeTX Manual](https://manual.edgetx.org/installing-and-updating-edgetx/updating-your-stm32h7-radio).
+            > Radios based on STM32H7 MCUs update differently to older radios. Do **not** use the "Flash via USB" option in EdgeTX Buddy with them (yet). To update radios such as the Flysky PA01 & ST16, Jumper T15 Pro, RM TX15, RM GX15 and RM TX16S MK3, please follow the instructions in the [EdgeTX Manual](https://manual.edgetx.org/installing-and-updating-edgetx/updating-your-stm32h7-radio).
 
             > [!NOTE]
             > For MacOS users, Companion is now only compiled for MacOS 12 and above. Stay with v2.10.5 or earlier if you need support for an older version of MacOS.