doc: add sxa GPG key (ed25519)

[sxa]

Part of nodejs/Release#733

Cc @nodejs/releasers

[aduh95]

The commit message doesn't meet our guidelines (you need to commit with both -S and -s). You'd need to also add an entry in the bash snippet below

node/README.md

Lines 797 to 806 in 242f2e7

	```bash
	gpg --keyserver hkps://keys.openpgp.org --recv-keys 5BE8A3F6C8A5C01D106C0AD820B1A390B168D356 # Antoine du Hamel
	gpg --keyserver hkps://keys.openpgp.org --recv-keys DD792F5973C6DE52C432CBDAC77ABFA00DDBF2B7 # Juan José Arboleda
	gpg --keyserver hkps://keys.openpgp.org --recv-keys CC68F5A3106FF448322E48ED27F5E38D5B0A215F # Marco Ippolito
	gpg --keyserver hkps://keys.openpgp.org --recv-keys 8FCCA13FEF1D0C2E91008E09770F7A9A5AE15600 # Michaël Zasso
	gpg --keyserver hkps://keys.openpgp.org --recv-keys 890C08DB8579162FEE0DF9DB8BEAB4DFCF555EF4 # Rafael Gonzaga
	gpg --keyserver hkps://keys.openpgp.org --recv-keys C82FA3AE1CBEDC6BE46B9360C43CEC45C17AB93C # Richard Lau
	gpg --keyserver hkps://keys.openpgp.org --recv-keys 108F52B48DB57BB0CC439B2997B01419BD92F80A # Ruy Adorno
	gpg --keyserver hkps://keys.openpgp.org --recv-keys A363A499291CBBC940DD62E41F10027AF002F8B0 # Ulises Gascón
	```

[aduh95]

If you can land it manually so the commit on main is signed with that key, it's a nice-to-have – but it's also fine if it's unsigned or signed by GH

[sxa]

If you can land it manually

Manually = with git node land -S yeah?

[sxa]

Landed in c713edd4e376

[richardlau]

Landed in c713edd4e376

Looks like it landed as 7ba71f7.