* Update script and intro an environment variable to using proxy for Github.
- Add `Dockerfile.rockylinux` to build Rocky Linux images
- Modify `pullsrc.sh`, add an environment variable to using proxy for Github.
- Modify `version.env`, sync environment variable.
- Modify `README.md`, sync doc.
- Modify `.github/workflows/build-images.yml`, sync Rocky Linux image.
* Update Dockerfile to enable build `openssh-askpass` package.
- Modify `Dockerfile.centos` / `Dockerfile.centos-stream` / `Dockerfile.rockylinux` to build `openssh-askpass` package.
* Update Dockerfile to fix lack requirement `imake` package.
- Modify `Dockerfile.centos` / `Dockerfile.centos-stream` to fix lack requirement `imake` package.
* Update Dockerfile to fix yum plugin error.
Try to fix:
```
No such command: config-manager. Please use /usr/bin/yum --help
It could be a YUM plugin command, try: "yum install dnf-command(config-manager)"
```
- Modify `Dockerfile.centos` / `Dockerfile.centos-stream` to fix error.
* Update Dockerfile to fix CentOS Stream 9 yum plugin error.
Try to fix:
```
Error: No matching repo to modify: powertools.
```
- Modify `Dockerfile.centos-stream` to fix error.
P.S: In CentOS 8 (with or without Stream), the package `imake` is included by `powertools` repository, and in CentOS Stream 9, the package is included by `crb` repository.
* Update Dockerfile to fix CentOS Stream 9 yum can not install `imake` error.
Try to fix:
```
Error: Unable to find a match: imake
```
- Modify `Dockerfile.centos-stream` to fix error.
P.S: In CentOS 8 (with or without Stream), the package `imake` is included by `powertools` repository, and in CentOS Stream 9, the package is included by ~~`crb`~~ `epel` repository.
* Update Dockerfile.centos-stream
Fix build error.
