Update receiver.html

[ot0tot]

It is not clear from the dropdown what FrSky / Futaba / Hitec and Spektrum / Graupner / JR refer to. This PR adds the channel map to the dropdown.
e.g. Spektrum / Graupner / JR becomes Spektrum / Graupner / JR (TAER1234)

[sonarqubecloud]

Quality Gate passed

Kudos, no new issues were introduced!

0 New issues
0 Security Hotspots
No data about Coverage
0.0% Duplication on New Code

See analysis details on SonarCloud

[haslinghuis]

Default is the same as second option (FrySky, Futaba, Hitec) 🤨

[github-actions]

Do you want to test this code? Here you have an automated build:
Betaflight-Configurator-Android
Betaflight-Configurator-Linux
Betaflight-Configurator-macOS
Betaflight-Configurator-Windows
WARNING: It may be unstable and result in corrupted configurations or data loss. Use only for testing!

[nerdCopter]

unsure this is needed. but does not hurt i suppose.
once selected the field already reports one or the other, rather conclusively.

[ot0tot]

unsure this is needed. but does not hurt i suppose. once selected the field already reports one or the other, rather conclusively.

Having the channel map appear in the list helps when providing support and asking the user to e.g. "change the channel map to AEETR1234". Especially for new users, it's not clear what to select.

Thanks for merging!