gitlab-ci.yml file prefix

[antonhinneck]

Hi,
PkgTemplates.jl suits my needs to generate new projects with CI pipeline perfectly.
However, I need to be able to make further modifications to gitlab-ci.yml files (set variables during package creation).
While a custom template could be created, addressing this directly in PkgTemplates.jl would be

• extremly straightforward and
• one would not have to maintain an additional template, beyond what is already in this package.

With this PR, one could exemplarily set the http_proxy using GitLabCI like so:

tpl = Template(;
    dir="./",
    host="host.com",
    user="antonhinneck",
    plugins=[Git(), 
    GitLabCI(;coverage=true,
    file_prefix="variables:\n\thttp_proxy: 10.0.0.1\n")]
)

tpl("Pkg.jl")

All tests pass. Would this be sensible for the scope of this package?

Best,
Anton

[codecov]

Codecov Report

Merging #372 (0d1d29e) into master (0de5d85) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #372   +/-   ##
=======================================
  Coverage   95.03%   95.03%           
=======================================
  Files          20       20           
  Lines         644      644           
=======================================
  Hits          612      612           
  Misses         32       32           

Impacted Files	Coverage Δ
src/plugins/ci.jl	97.46% <ø> (ø)

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[gdalle]

I don't see a reason not to accept this. Can you add documentation and tests for this? The reference tests compare generated packages to a series of "fixtures", and they are only run for Julia 1.7.2. I suggest you modify the WackyOptions test suite accordingly