update node to v20 lts

[akellbl4]

• updates node to v20
• enable use of pnpm v8
• replaces nvmrc with npmrc (pnpm manages node version for you)
• moves env requirements to the root package.json

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (82c6178) 61.47% compared to head (6917ad0) 61.47%. Report is 1 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1688 +/- ## ======================================= Coverage 61.47% 61.47% ======================================= Files 132 132 Lines 2998 2998 Branches 757 757 ======================================= Hits 1843 1843 Misses 1038 1038 Partials 117 117 ```

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[github-actions[bot]]

size-limit report 📦

Path	Size
public/embed.mjs	2.03 KB (0%)
public/remark.mjs	73.45 KB (-0.01% 🔽)
public/remark.css	8.26 KB (-0.04% 🔽)
public/last-comments.mjs	35.72 KB (-0.01% 🔽)
public/last-comments.css	3.75 KB (0%)
public/deleteme.mjs	12.07 KB (0%)
public/counter.mjs	751 B (0%)

[github-actions[bot]]

Pull Request Test Coverage Report for Build 7623478702

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.06%) to 84.833%

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Totals
Change from base Build 7596391691:	0.06%
Covered Lines:	5968
Relevant Lines:	7035

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💛 - Coveralls