fix: rendering of MIRROR_FUNCS.md on GitHub

[alexandear]

This PR fixes displaying of the MIRROR_FUNCS.md on GitHub. Also, adds the comment that MIRROR_FUNCS.md is @generated and should not be edited manually.

Before:

After:

[coveralls]

Pull Request Test Coverage Report for Build 11889567228

Details

• 0 of 6 (0.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.2%) to 39.43%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
cmd/internal/mirror-table/main.go	0	6	0.0%

Totals
Change from base Build 10106851310:	-0.2%
Covered Lines:	263
Relevant Lines:	667

---

💛 - Coveralls

[butuzov]

I wish i could remember reason why did I wend with table, and not markdown. Let it hang for a few days i will try update this PR asap.