ci: add spellcheck.dic validation

[drink7036290]

Motivation

As per #7061, the spellcheck.dic file had an incorrect word count.

Solution

This PR corrects the word count in spellcheck.dic and adds a new validation step in ci.yml to prevent similar issues in the future. The validation checks that:

1. The first line is an integer.
2. The last line is completely empty (no spaces).
3. The number of lines between the first and last matches the integer specified in the first line.

Fixes: #7061

[Darksonn]

This file currently ends with two newline characters rather than one. Is that intentional?

$ hexdump spellcheck.dic
0000000 3932 0a39 0a26 0a2b 0a3c 0a3d 0a3e 0a5c
...
0000900 656b 7075 0a73 6f77 6b72 7473 6165 696c
0000910 676e 0a0a
0000914

Note that 0a is a newline character.

[drink7036290]

Maybe it's the displaying arrangement by hexdump with or without the "-C" option ?

Though these two "0a" sit at different positions shown below, they all have the same appearance: a last empty line.

$ cat -A spellcheck.dic | tail -3
wakeups$
workstealing$
$

// commit da745ff, the last commit that pass the validations

$ hexdump spellcheck.dic | tail -3
00008c0 6b61 7565 7370 770a 726f 736b 6574 6c61
00008d0 6e69 0a67 000a                         
00008d5
$ hexdump -C spellcheck.dic | tail -3
000008c0  61 6b 65 75 70 73 0a 77  6f 72 6b 73 74 65 61 6c  |akeups.worksteal|
000008d0  69 6e 67 0a 0a                                    |ing..|
000008d5

// current PR

$ hexdump spellcheck.dic | tail -3
0000900 656b 7075 0a73 6f77 6b72 7473 6165 696c
0000910 676e 0a0a                              
0000914
$ hexdump -C spellcheck.dic | tail -3
00000900  6b 65 75 70 73 0a 77 6f  72 6b 73 74 65 61 6c 69  |keups.worksteali|
00000910  6e 67 0a 0a                                       |ng..|
00000914

Thanks for the reminding, I'm also wonder why hexdump will reorder char's position while no "-C" option, take the word "workstealing" as an example:

00008c0 6b61 7565 7370 770a 726f 736b 6574 6c61
                        w\n  r o  s k  e t  l a
00008d0 6e69 0a67 000a
         n i \n g   \n