feat: grant team lead maintainer permissions on team create

[no-or]

team: grant team lead maintainer permissions on github team

Closes #547

Details

Before the change:
cmd: /rocket team create <team-name> --lead noor
result: noor is added to lead but not as a maintainer of the team

After the change:
cmd: /rocket team create <team-name> --lead noor
result: noor is added to lead who is also a maintainer of the team

[codecov]

Codecov Report

Merging #595 (142d379) into master (eb95e33) will decrease coverage by 0.10%.
The diff coverage is 57.14%.

@@            Coverage Diff             @@
##           master     #595      +/-   ##
==========================================
- Coverage   93.09%   92.98%   -0.11%     
==========================================
  Files          42       42              
  Lines        2420     2425       +5     
  Branches      323      323              
==========================================
+ Hits         2253     2255       +2     
- Misses        109      112       +3     
  Partials       58       58              

Impacted Files	Coverage Δ
interface/github.py	94.35% <40.00%> (-2.29%)	⬇️
app/controller/command/commands/team.py	86.35% <100.00%> (ø)

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[chuck-sys]

(Later task): make it so that leads themselves don't have to specify themselves in --leads. I'd be pretty annoyed if I have to do that every time without tab-complete.