Add update option

[strangelookingnerd]

What does this PR aim to accomplish?:

Add an option to manually update PADD if there is a new version available.

How does this PR accomplish the above?:

Add new -u | --update option that updates the script if there is a new version available using wget or curl.

Link documentation PRs if any are needed to support this PR:

README.md has been updated.

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[strangelookingnerd]

Please understand that I'm by no means an expert for Shell, so any suggestions are welcome 😄

[yubiuser]

Please target development branch instead of master

[github-actions]

This pull request has conflicts, please resolve those before we can evaluate the pull request.

[github-actions]

Conflicts have been resolved.

[yubiuser]

Currently, the output looks like

pi@s740:~$ ./padd.sh -u
[i] Updates are available
[i] Downloading via wget ...
--2023-04-14 15:52:36--  https://install.padd.sh/
Resolving install.padd.sh (install.padd.sh)... 52.33.207.7, 44.230.85.241
Connecting to install.padd.sh (install.padd.sh)|52.33.207.7|:443... connected.
HTTP request sent, awaiting response... 307 Temporary Redirect
Location: https://raw.githubusercontent.com/pi-hole/PADD/master/padd.sh [following]
--2023-04-14 15:52:37--  https://raw.githubusercontent.com/pi-hole/PADD/master/padd.sh
Resolving raw.githubusercontent.com (raw.githubusercontent.com)... 185.199.110.133, 185.199.108.133, 185.199.111.133, ...
Connecting to raw.githubusercontent.com (raw.githubusercontent.com)|185.199.110.133|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 63631 (62K) [text/plain]
Saving to: '/home/pi/padd.sh'

/home/pi/padd.sh                                       100%[=========================================================================================================================>]  62.14K  --.-KB/s    in 0.02s   

2023-04-14 15:52:37 (2.79 MB/s) - '/home/pi/padd.sh' saved [63631/63631]

[✓] ... done. Restart PADD for the update to take effect

• I'm not sure if we should keep all the wget (and curl) output or suppress it?
• Also there is no error handling at the moment if downloading fails for any reason.
• You might want to show the current and the new version as well?

[strangelookingnerd]

I'm not sure if we should keep all the wget (and curl) output or suppress it?

I decided to suppress the output. Looks cleaner that way. Could still be reverted if you think otherwise.

Also there is no error handling at the moment if downloading fails for any reason.

I added some error handling, let me know what you think.

You might want to show the current and the new version as well?

That is a great idea, added it as well.

[yubiuser]

Looks nicer now

pi@s740:~$ ./padd.sh -u
[i] Updating PADD from v3.09.1 to v3.10.1
[i] Downloading PADD update via wget ...
[✓] ... done. Restart PADD for the update to take effect

[yubiuser]

Looks good from my side.
Please rebase on latest development and squash all commits down.

[strangelookingnerd]

Re-created PR to squash commits in #352