chore!: drop support for Node 13, 14.0.0-14.13.1 and 15

[ehmicky]

From the discussion at netlify/netlify-headers-parser#80 (comment)

Discussing with @lukasholzer and @JGAntunes we decided to drop support for Node 13, 15 and 14 below 14.14.0.

This will require a major release and editing our previous announcement.

---

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[github-actions]

📊 Benchmark results

Comparing with 08323af

Package size: 365 MB

⬇️ 0.00% decrease vs. 08323af

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└───┴──┴────┴──┴────┴──┴────┴──┴────┴──┴────┴──┴────┴──┴────┴──┴────┴──┴────┴──┴────┴──┴────┴──┴────┴──┴──>
    T-12    T-11    T-10    T-9     T-8     T-7     T-6     T-5     T-4     T-3     T-2     T-1      T    

Legend

• T-30 (08323af): 365 MB
• T-29 (ba154f6): 365 MB
• T-28 (51bde9a): 365 MB
• T-27 (53643b4): 365 MB
• T-26 (bb09481): 365 MB
• T-25 (f7ca0d1): 365 MB
• T-24 (65cf7cc): 365 MB
• T-23 (e2ef338): 365 MB
• T-22 (134e441): 365 MB
• T-21 (4357279): 365 MB
• T-20 (2effcdb): 364 MB
• T-19 (0fcf5ec): 364 MB
• T-18 (e87d1e1): 364 MB
• T-17 (eaeced2): 364 MB
• T-16 (b2f77f3): 364 MB
• T-15 (e47ded9): 364 MB
• T-14 (fc3cecb): 364 MB
• T-13 (8ad90d0): 364 MB
• T-12 (cf1d3f1): 364 MB
• T-11 (e690ee5): 364 MB
• T-10 (a894ef4): 364 MB
• T-9 (86ffb8a): 364 MB
• T-8 (5f59329): 364 MB
• T-7 (4b49ca8): 364 MB
• T-6 (618d997): 364 MB
• T-5 (5272de7): 364 MB
• T-4 (86931c6): 364 MB
• T-3 (a875fb7): 364 MB
• T-2 (05fe45a): 364 MB
• T-1 (089d65e): 365 MB
• T (current commit): 365 MB

[lukasholzer]

thx for taking care of it ❤️