chore: add git in Docker Image

[MaineK00n]

What did you implement:

I think it would be good to have git installed for GitHubRepos fetch.

Type of change

• New feature (non-breaking change which adds functionality)

How Has This Been Tested?

$ docker run --rm vuls/go-exploitdb:latest fetch githubrepos
Unable to find image 'vuls/go-exploitdb:latest' locally
latest: Pulling from vuls/go-exploitdb
Digest: sha256:90c7d3a7c5fc6636a024c1eb33bb23f856e1d170d6c4f6ed11e6d619f1ea6f7e
Status: Downloaded newer image for vuls/go-exploitdb:latest
t=2022-03-24T23:51:16+0000 lvl=info msg="Fetching GitHub Repos Exploit"
t=2022-03-24T23:51:16+0000 lvl=warn msg="Recommend installing git (if not, DB update is very slow)"
t=2022-03-24T23:51:41+0000 lvl=info msg="GitHub Repos Exploit" count=2808
t=2022-03-24T23:51:41+0000 lvl=info msg="Insert Exploit into go-exploitdb." db=sqlite3
t=2022-03-24T23:51:41+0000 lvl=info msg="Inserting 2808 Exploits"
t=2022-03-24T23:51:41+0000 lvl=info msg="Inserting new Exploits"
2808 / 2808 [------------------------------------------------------------------------] 100.00% ? p/st=2022-03-24T23:51:41+0000 lvl=info msg="No CveID Exploit Count" count=0
t=2022-03-24T23:51:41+0000 lvl=info msg="CveID Exploit Count" count=2808

$ docker build -t vuls/go-exploitdb:pr .
$ docker run --rm vuls/go-exploitdb:pr fetch githubrepos
t=2022-03-24T23:50:50+0000 lvl=info msg="Fetching GitHub Repos Exploit"
t=2022-03-24T23:50:52+0000 lvl=info msg="GitHub Repos Exploit" count=2808
t=2022-03-24T23:50:52+0000 lvl=info msg="Insert Exploit into go-exploitdb." db=sqlite3
t=2022-03-24T23:50:52+0000 lvl=info msg="Inserting 2808 Exploits"
t=2022-03-24T23:50:52+0000 lvl=info msg="Inserting new Exploits"
2808 / 2808 [------------------------------------------------------------------------] 100.00% ? p/st=2022-03-24T23:50:52+0000 lvl=info msg="No CveID Exploit Count" count=0
t=2022-03-24T23:50:52+0000 lvl=info msg="CveID Exploit Count" count=2808

Checklist:

You don't have to satisfy all of the following.

• Write tests
• Write documentation
• Check that there aren't other open pull requests for the same issue/feature
• Format your source code by make fmt
• Pass the test by make test
• Provide verification config / commands
• Enable "Allow edits from maintainers" for this PR
• Update the messages below

Is this ready for review?: YES

Reference