* Update the installation of MMCV * use matrix.torch_version * fix typo in doc * fix docs * fix colab * change docs
* change version to v0.21.0 * change version to v0.21.0 * change version to v0.21.0 * change version to v0.21.0
* merge docs/ and docs_zh-CN/ * merge docs/ and docs_zh-CN/ * merge docs/ and docs_zh-CN/ * merge docs/ and docs_zh-CN/ * fix launch utility url * fix launch utility url * fix wrong pytorch doc url * remove wrong links docs//