docs: add C++ support chapter to the API guides

docs/en/api-guides/index.rst

@@ -10,7 +10,9 @@ API Guides
    :SOC_BT_SUPPORTED: blufi
    bootloader
    build-system
+   :SOC_SUPPORT_COEXISTENCE: coexist
    core_dump
+   cplusplus
    :SOC_RTC_MEM_SUPPORTED: deep-sleep-stub
    :SOC_USB_OTG_SUPPORTED: dfu
    error-handling
@@ -18,6 +20,7 @@ API Guides
    freertos-smp
    :SOC_WIFI_MESH_SUPPORT: esp-wifi-mesh
    event-handling
+   :SOC_SPIRAM_SUPPORTED: external-ram
    fatal-errors
    ../security/flash-encryption
    :esp32s3: flash_psram_config
@@ -30,10 +33,10 @@ API Guides
    openthread
    partition-tables
    performance/index
+   reproducible-builds
    :not esp32c6: RF_calibration
    :esp32: ../security/secure-boot-v1
    ../security/secure-boot-v2
-   :SOC_SPIRAM_SUPPORTED: external-ram
    thread-local-storage
    tools/index
    unit-tests
@@ -42,5 +45,3 @@ API Guides
    :SOC_USB_SERIAL_JTAG_SUPPORTED: usb-serial-jtag-console
    :SOC_WIFI_SUPPORTED: wifi
    :SOC_WIFI_SUPPORTED: wifi-security
-   :SOC_SUPPORT_COEXISTENCE: coexist
-   reproducible-builds