[docs] dark theme support and full image paths (#7110)

README.md

@@ -15,7 +15,7 @@ OpenThread released by Google is... <a href="https://www.threadgroup.org/What-is
 More information about Thread can be found at [threadgroup.org](http://threadgroup.org/). Thread is a registered trademark of the Thread Group, Inc.
 
 [ot-repo]: https://github.com/openthread/openthread
-[ot-logo]: doc/images/openthread_logo.png
+[ot-logo]: https://github.com/openthread/openthread/raw/main/doc/images/openthread_logo.png
 [ot-gh-action-build]: https://github.com/openthread/openthread/actions?query=workflow%3ABuild+branch%3Amain+event%3Apush
 [ot-gh-action-build-svg]: https://github.com/openthread/openthread/workflows/Build/badge.svg?branch=main&event=push
 [ot-gh-action-simulation]: https://github.com/openthread/openthread/actions?query=workflow%3ASimulation+branch%3Amain+event%3Apush
@@ -29,7 +29,7 @@ More information about Thread can be found at [threadgroup.org](http://threadgro
 
 # Who supports OpenThread?
 
-<a href="https://www.arm.com/"><img src="doc/images/ot-contrib-arm.png" alt="ARM" width="200px"></a><a href="https://www.cascoda.com/"><img src="doc/images/ot-contrib-cascoda.png" alt="Cascoda" width="200px"></a><a href="https://www.espressif.com/"><img src="doc/images/ot-contrib-espressif-github.png" alt="Espressif" width="200px"></a><a href="https://www.google.com/"><img src="doc/images/ot-contrib-google.png" alt="Google" width="200px"></a><a href="http://www.nordicsemi.com/"><img src="doc/images/ot-contrib-nordic.png" alt="Nordic" width="200px"></a><a href="http://www.nxp.com/"><img src="doc/images/ot-contrib-nxp.png" alt="NXP" width="200px"></a><a href="http://www.qorvo.com/"><img src="doc/images/ot-contrib-qorvo.png" alt="Qorvo" width="200px"></a><a href="https://www.qualcomm.com/"><img src="doc/images/ot-contrib-qc.png" alt="Qualcomm" width="200px"></a><a href="https://www.samsung.com/"><img src="doc/images/ot-contrib-samsung.png" alt="Samsung" width="200px"></a><a href="https://www.silabs.com/"><img src="doc/images/ot-contrib-silabs.png" alt="Silicon Labs" width="200px"></a><a href="https://www.st.com/"><img src="doc/images/ot-contrib-stm.png" alt="STMicroelectronics" width="200px"></a><a href="https://www.synopsys.com/"><img src="doc/images/ot-contrib-synopsys.png" alt="Synopsys" width="200px"></a><a href="https://www.telink-semi.com/"><img src="doc/images/ot-contrib-telink-github.png" alt="Telink Semiconductor" width="200px"></a><a href="https://www.ti.com/"><img src="doc/images/ot-contrib-ti.png" alt="Texas Instruments" width="200px"></a><a href="https://www.zephyrproject.org/"><img src="doc/images/ot-contrib-zephyr.png" alt="Zephyr Project" width="200px"></a>
+<a href="https://www.arm.com/"><img src="https://github.com/openthread/openthread/raw/main/doc/images/ot-contrib-arm.png" alt="ARM" width="200px"></a><a href="https://www.cascoda.com/"><img src="https://github.com/openthread/openthread/raw/main/doc/images/ot-contrib-cascoda.png" alt="Cascoda" width="200px"></a><a href="https://www.espressif.com/"><img src="https://github.com/openthread/openthread/raw/main/doc/images/ot-contrib-espressif-github.png" alt="Espressif" width="200px"></a><a href="https://www.google.com/"><img src="https://github.com/openthread/openthread/raw/main/doc/images/ot-contrib-google.png" alt="Google" width="200px"></a><a href="http://www.nordicsemi.com/"><img src="https://github.com/openthread/openthread/raw/main/doc/images/ot-contrib-nordic.png" alt="Nordic" width="200px"></a><a href="http://www.nxp.com/"><img src="https://github.com/openthread/openthread/raw/main/doc/images/ot-contrib-nxp.png" alt="NXP" width="200px"></a><a href="http://www.qorvo.com/"><img src="https://github.com/openthread/openthread/raw/main/doc/images/ot-contrib-qorvo.png" alt="Qorvo" width="200px"></a><a href="https://www.qualcomm.com/"><img src="https://github.com/openthread/openthread/raw/main/doc/images/ot-contrib-qc.png" alt="Qualcomm" width="200px"></a><a href="https://www.samsung.com/"><img src="https://github.com/openthread/openthread/raw/main/doc/images/ot-contrib-samsung.png" alt="Samsung" width="200px"></a><a href="https://www.silabs.com/"><img src="https://github.com/openthread/openthread/raw/main/doc/images/ot-contrib-silabs.png" alt="Silicon Labs" width="200px"></a><a href="https://www.st.com/"><img src="https://github.com/openthread/openthread/raw/main/doc/images/ot-contrib-stm.png" alt="STMicroelectronics" width="200px"></a><a href="https://www.synopsys.com/"><img src="https://github.com/openthread/openthread/raw/main/doc/images/ot-contrib-synopsys.png" alt="Synopsys" width="200px"></a><a href="https://www.telink-semi.com/"><img src="https://github.com/openthread/openthread/raw/main/doc/images/ot-contrib-telink-github.png" alt="Telink Semiconductor" width="200px"></a><a href="https://www.ti.com/"><img src="https://github.com/openthread/openthread/raw/main/doc/images/ot-contrib-ti.png" alt="Texas Instruments" width="200px"></a><a href="https://www.zephyrproject.org/"><img src="https://github.com/openthread/openthread/raw/main/doc/images/ot-contrib-zephyr.png" alt="Zephyr Project" width="200px"></a>
 
 # Getting started