Use larger titles in issue templates

[JSAbrahams]

Just looks better, more horizontal separators.

[codecov[bot]]

Codecov Report

Merging #441 (f172b06) into develop (9723d5f) will increase coverage by 0.18%. The diff coverage is n/a.

@@             Coverage Diff             @@
##           develop     #441      +/-   ##
===========================================
+ Coverage    88.43%   88.62%   +0.18%     
===========================================
  Files          110      110              
  Lines        12040    11936     -104     
===========================================
- Hits         10648    10578      -70     
+ Misses        1392     1358      -34     

Impacted Files	Coverage Δ
src/check/constrain/unify/ty.rs	76.13% <0.00%> (-7.91%)	:arrow_down:
src/check/constrain/generate/class.rs	81.48% <0.00%> (-7.65%)	:arrow_down:
src/check/result.rs	75.55% <0.00%> (-6.67%)	:arrow_down:
src/check/constrain/unify/function.rs	78.83% <0.00%> (-2.65%)	:arrow_down:
src/check/constrain/generate/collection.rs	94.25% <0.00%> (-2.49%)	:arrow_down:
src/check/constrain/constraint/iterator.rs	84.61% <0.00%> (-2.06%)	:arrow_down:
src/check/constrain/generate/control_flow.rs	91.95% <0.00%> (-1.51%)	:arrow_down:
src/parse/mod.rs	70.00% <0.00%> (-1.43%)	:arrow_down:
src/parse/expression.rs	93.85% <0.00%> (-0.88%)	:arrow_down:
src/generate/ast/node.rs	76.51% <0.00%> (-0.76%)	:arrow_down:
... and 47 more