Update README.md

[SkymanOne]

Update ink! doc link and removes mention of Canvas since the project has been archived

[HCastano]

It looks like there's still other uses of ink.substrate.io in the codebase. Can you replace those as well (aside from maybe the one in the monthly update)?

[codecov-commenter]

Codecov Report

Merging #1521 (b7aa5f8) into master (dc62b4f) will decrease coverage by 6.67%.
The diff coverage is n/a.

❗ Current head b7aa5f8 differs from pull request most recent head 05af29f. Consider uploading reports for the commit 05af29f to get more accurate results

@@            Coverage Diff             @@
##           master    #1521      +/-   ##
==========================================
- Coverage   71.73%   65.06%   -6.68%     
==========================================
  Files         204      204              
  Lines        6316     6314       -2     
==========================================
- Hits         4531     4108     -423     
- Misses       1785     2206     +421     

Impacted Files	Coverage Δ
crates/ink/ir/src/ir/contract.rs	0.00% <0.00%> (-100.00%)	⬇️
crates/ink/ir/src/ir/ink_test.rs	0.00% <0.00%> (-87.50%)	⬇️
crates/ink/ir/src/ir/trait_def/mod.rs	0.00% <0.00%> (-81.82%)	⬇️
crates/ink/ir/src/ir/storage_item/mod.rs	0.00% <0.00%> (-73.92%)	⬇️
crates/ink/ir/src/ir/storage_item/config.rs	0.00% <0.00%> (-73.34%)	⬇️
crates/ink/ir/src/ir/blake2.rs	20.83% <0.00%> (-58.34%)	⬇️
crates/ink/ir/src/ir/trait_def/config.rs	7.14% <0.00%> (-57.15%)	⬇️
crates/ink/ir/src/ir/trait_def/item/trait_item.rs	45.90% <0.00%> (-45.91%)	⬇️
crates/ink/ir/src/ir/config.rs	64.00% <0.00%> (-36.00%)	⬇️
crates/ink/ir/src/ir/utils.rs	57.40% <0.00%> (-35.19%)	⬇️
... and 21 more

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