simple integration test

[yegor256]

See #3. Based on #22

This PR implements a simple integration test, where you inject your own normalization step

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PR-Codex overview

Detailed summary

• Added before.txt and after.txt files to .gitignore.
• Added app.eo file to .gitignore.
• Ignored .bak files.
• Updated eo-phi-normalizer/src/Language/EO/Phi/Syntax/Lex.hs file.
• Updated eo-phi-normalizer/src/Language/EO/Phi/Syntax/Par.hs file.
• Updated eo-phi-normalizer/src/Language/EO/Phi/Syntax/Par.y file.
• Updated eo-phi-normalizer/src/Language/EO/Phi/Syntax/Print.hs file.
• Updated eo-phi-normalizer/src/Language/EO/Phi/Syntax/Abs.hs file.
• Updated .github/workflows/ghc.yml file.
• Updated pipeline.sh file.
• Updated eo-phi-normalizer/grammar/EO/Phi/Syntax.cf file.
• Updated eo-phi-normalizer/src/Language/EO/Phi/Syntax/Lex.x file.
• Added pipeline directory.
• Added app.eo file to pipeline directory.
• Updated pipeline.sh file.
• Updated eo-phi-normalizer/src/Language/EO/Phi/Syntax/Doc.txt file.

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[deemp]

Blocked on #14. Normalizer can't parse.

Source EO code

[args] > app
  QQ.io.stdout > @
    "Hello, world!\n"

$\varphi$-expression

{app ↦ ⟦args ↦ ∅, φ ↦ Φ.org.eolang.io.stdout(α0 ↦ Φ.org.eolang.string(α0 ↦ Φ.org.eolang.bytes(Δ ⤍ 48-65-6C-6C-6F-2C-20-77-6F-72-6C-64-21-0A)))⟧}

[fizruk]

Superseded by #24.