github/workflow: update go to 1.20 and neovim to v0.8.3

[codecov[bot]]

Codecov Report

Merging #152 (d179209) into main (1762f7f) will increase coverage by 0.6%. The diff coverage is 100.0%.

@@           Coverage Diff           @@
##            main    #152     +/-   ##
=======================================
+ Coverage   82.5%   83.2%   +0.6%     
=======================================
  Files         14      14             
  Lines       3120    3118      -2     
=======================================
+ Hits        2577    2596     +19     
+ Misses       543     522     -21     

Flag	Coverage Δ
linux-1.17-stable	?
linux-1.18-nightly	83.2% <100.0%> (?)
linux-1.18-stable	83.2% <100.0%> (+0.6%)	:arrow_up:
linux-1.19-nightly	83.2% <100.0%> (?)
linux-1.19-stable	83.2% <100.0%> (+0.6%)	:arrow_up:
linux-1.20-nightly	83.2% <100.0%> (?)
linux-1.20-stable	83.2% <100.0%> (?)
macos-1.17-stable	?
macos-1.18-nightly	83.2% <100.0%> (?)
macos-1.18-stable	83.2% <100.0%> (+0.6%)	:arrow_up:
macos-1.19-nightly	83.2% <100.0%> (?)
macos-1.19-stable	83.2% <100.0%> (+0.6%)	:arrow_up:
macos-1.20-nightly	83.2% <100.0%> (?)
macos-1.20-stable	83.2% <100.0%> (?)
windows-1.17-stable	?
windows-1.18-stable	82.4% <100.0%> (+0.6%)	:arrow_up:
windows-1.19-nightly	82.4% <100.0%> (?)
windows-1.19-stable	82.4% <100.0%> (+0.6%)	:arrow_up:
windows-1.20-nightly	82.4% <100.0%> (?)
windows-1.20-stable	82.4% <100.0%> (?)

Impacted Files	Coverage Δ
nvim/nvim.go	78.8% <100.0%> (-0.8%)	:arrow_down:

... and 1 file with indirect coverage changes