Language improvements + Make CI spellcheck examples/*

[cmichi]

I found that our CI didn't actually check the examples/ subfolders.

[codecov-commenter]

Codecov Report

Merging #1264 (c25ff94) into master (8ffb7c0) will increase coverage by 16.41%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           master    #1264       +/-   ##
===========================================
+ Coverage   62.32%   78.74%   +16.41%     
===========================================
  Files         227      228        +1     
  Lines        8645     8675       +30     
===========================================
+ Hits         5388     6831     +1443     
+ Misses       3257     1844     -1413     

Impacted Files	Coverage Δ
...ates/storage/src/collections/hashmap/fuzz_tests.rs	95.74% <0.00%> (-4.26%)	⬇️
crates/allocator/src/bump.rs	0.00% <0.00%> (ø)
crates/lang/ir/src/ir/attrs.rs	82.27% <0.00%> (+3.60%)	⬆️
crates/lang/ir/src/ir/trait_def/item/mod.rs	90.16% <0.00%> (+4.91%)	⬆️
crates/lang/ir/src/ir/item_impl/constructor.rs	93.84% <0.00%> (+6.15%)	⬆️
crates/lang/ir/src/ir/idents_lint.rs	71.42% <0.00%> (+9.52%)	⬆️
crates/engine/src/ext.rs	70.17% <0.00%> (+14.03%)	⬆️
crates/lang/ir/src/ir/item_impl/callable.rs	91.91% <0.00%> (+14.14%)	⬆️
crates/lang/ir/src/ir/item_impl/message.rs	92.13% <0.00%> (+14.60%)	⬆️
crates/lang/ir/src/ir/selector.rs	88.00% <0.00%> (+16.00%)	⬆️
... and 40 more

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[paritytech-cicd-pr]

🦑 📈 ink! Example Contracts ‒ Changes Report 📉 🦑

These are the results when building the examples/* contracts from this branch with cargo-contract 1.3.0-cef152e and comparing them to ink! master:

	Δ Optimized Size	Δ Used Gas	Total Optimized Size	Total Used Gas
accumulator			1.04 K
adder			2.13 K
contract-introspection			2.37 K
contract-terminate			0.94 K	275_000
contract-transfer			8.13 K	75_000
data-structures			1.73 K
delegate-calls			2.96 K	76_276
delegator			6.38 K	232_281
dns			8.89 K	225_000
erc1155			17.30 K	450_000
erc20			8.49 K	225_000
erc721			11.82 K	600_000
flipper			1.31 K	75_000
forward-calls			2.88 K	151_427
incrementer			1.21 K
mother			12.41 K
multisig			25.12 K	470_156
rand-extension			3.92 K	75_000
seal-code-hash			1.58 K
seal-ecdsa			1.81 K
set-code-hash			1.57 K	150_000
subber			2.15 K
trait-erc20			8.77 K	225_000
trait-flipper			1.00 K	75_000
trait-incrementer			1.19 K	150_000
updated-incrementer			9.62 K
upgradeable-flipper			1.55 K

Link to the run | Last update: Thu May 19 15:03:50 CEST 2022