chore: bump guide node 18

[ICEPrey]

Please describe the changes this PR makes and why it should be merged:

Changes Made

1. Updated the minimum required Node.js version for discord.js v14 from v16.11.0 to v18.20.4 on the guide.
2. Modified the version check example in the tip section, changing the version number from v16.11.0 to v18.20.4.

Reasons for Merging

1. Documentation Accuracy: Keeps the documentation up-to-date with the current requirements for using discord.js v14.
2. Best Practices: Aligns with current best practices by recommending a more recent LTS version of Node.js.
3. User Experience: Helps prevent potential issues users might encounter when trying to use discord.js with an outdated Node.js version.

Status and versioning classification:

• This PR only includes non-code changes, like changes to documentation, README, etc.

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[vladfrangu]

Imo for the guide we should guide people towards newer LTS versions, even if libraries may support older ones. Node 18 is set to become EoL this october if memory serves, might as well document node 20 here

[ICEPrey]

Got it will do tomorrow.

[almeidx]

I'm not sure this guide is supposed to receive updates, cc: @iCrawl

Either way, Node.js v18 becomes end-of-life on 2025-04-30, not this october
If we're going to update this, might as well use Node.js v22 which starts LTS at 2024-10-29, <2 months away (Node.js v20 goes into maintenance a day after that)

[ICEPrey]

I'm not sure this guide is supposed to receive updates, cc: @iCrawl

Either way, Node.js v18 becomes end-of-life on 2025-04-30, not this october If we're going to update this, might as well use Node.js v22 which starts LTS at 2024-10-29, <2 months away (Node.js v20 goes into maintenance a day after that)

Oh ok so before proceeding, I'd like to address a couple of points

@almeidx: Thank you for the correction on Node.js v18's end-of-life date and the suggestion for v22. You've raised an important question about whether this guide is supposed to receive updates

@iCrawl: Could you please clarify if this guide is meant to receive regular updates?

If the guide is supposed to get regular updates, are we suppose to update the minimum required Node.js version from v16.11.0 to v22.8.0 (Current version). Or should we prioritize the Current version (v22.8.0) or the LTS version (v20.17.0) in our recommendations?