update readme

[pawelru]

• remove r-universe install instructions for simplicity
• remove r-universe link - this fixes url-checker

[github-actions]

✅ All contributors have signed the CLA
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[pawelru]

I have read the CLA Document and I hereby sign the CLA

[github-actions]

Code Coverage Summary

Filename                 Stmts    Miss  Cover    Missing
---------------------  -------  ------  -------  ---------
R/qenv-concat.R             10       0  100.00%
R/qenv-constructor.R        16      13  18.75%   54-93
R/qenv-eval_code.R          52       2  96.15%   100, 109
R/qenv-get_code.R           20       1  95.00%   38
R/qenv-get_env.R             3       3  0.00%    23-31
R/qenv-get_var.R            19       0  100.00%
R/qenv-get_warnings.R       24       0  100.00%
R/qenv-join.R               46       0  100.00%
R/qenv-show.R                1       1  0.00%    19
R/qenv-within.R              8       0  100.00%
R/utils.R                   10       0  100.00%
TOTAL                      209      20  90.43%

Diff against main

Filename      Stmts    Miss  Cover
----------  -------  ------  --------
TOTAL             0       0  +100.00%

Results for commit: d3506c5

Minimum allowed coverage is 80%

♻️ This comment has been updated with latest results

[github-actions]

Unit Tests Summary

  1 files    9 suites   0s ⏱️
 62 tests  62 ✅ 0 💤 0 ❌
134 runs  134 ✅ 0 💤 0 ❌

Results for commit d3506c5.

[github-actions]

Unit Tests Summary

  1 files    9 suites   0s ⏱️
 62 tests  62 ✅ 0 💤 0 ❌
134 runs  134 ✅ 0 💤 0 ❌

Results for commit d3506c5.