Bump minimum needed R version to 3.6

[IndrajeetPatil]

R 4.3 is scheduled for release on April 21.

Follow-up on #985

[github-actions]

This is how benchmark results would change (along with a 95% confidence interval in relative change) if 57bbf4e is merged into main:

• ❗🐌cache_applying: 76ms -> 80ms [+3.5%, +7.09%]
•   :ballot_box_with_check:cache_recording: 1.04s -> 1.03s [-1.41%, +1.01%]
•   :ballot_box_with_check:without_cache: 2.5s -> 2.5s [-0.72%, +0.78%]

Further explanation regarding interpretation and methodology can be found in the documentation.

[codecov-commenter]

Codecov Report

Merging #1101 (5001fb9) into main (15a5f5b) will increase coverage by 1.08%.
The diff coverage is 80.00%.

❗ Current head 5001fb9 differs from pull request most recent head 6045bee. Consider uploading reports for the commit 6045bee to get more accurate results

@@            Coverage Diff             @@
##             main    #1101      +/-   ##
==========================================
+ Coverage   91.07%   92.16%   +1.08%     
==========================================
  Files          46       46              
  Lines        2701     2654      -47     
==========================================
- Hits         2460     2446      -14     
+ Misses        241      208      -33     

Impacted Files	Coverage Δ
R/environments.R	0.00% <0.00%> (-100.00%)	⬇️
R/parse.R	87.65% <ø> (-0.16%)	⬇️
R/style-guides.R	100.00% <ø> (+0.56%)	⬆️
R/nest.R	100.00% <100.00%> (ø)
R/relevel.R	96.87% <100.00%> (+47.57%)	⬆️

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[github-actions]

This is how benchmark results would change (along with a 95% confidence interval in relative change) if 15a5f5b is merged into main:

•   :ballot_box_with_check:cache_applying: 245ms -> 247ms [-1.53%, +3.2%]
•   :ballot_box_with_check:cache_recording: 746ms -> 744ms [-1.69%, +1.07%]
•   :ballot_box_with_check:without_cache: 1.37s -> 1.38s [-1.18%, +1.71%]

Further explanation regarding interpretation and methodology can be found in the documentation.

[lorenzwalthert]

LGTM, thanks @IndrajeetPatil 🥳