Correct the README tables, document the rules, and add a checker that keeps them correct

[hingston]

Fixes #294.

Sizes that did not match the solution files

Row	Was	Now
Year 11 Injection Sites 1 (speed)	21	18
Year 12 Unzip (speed)	8	19
Year 25 My First Shredding Memory (speed)	47	9
Year 47 Automated Pleasantries (speed)	3	34
Year 50 Cubical Communication (speed)	12	31
Year 59 Glory Hole (speed)	9	144
Year 23 Sorting Hall (<50%, speed)	10	23

Credit

• Year 19 Content Creators Bug Fix: n05ucc4u, who replaced the solution with the current three command version in
  4c7247f. The table still credited the older solution.
• Year 65 Defrag Ordered (size): commonnickname, who improved it to 14i/369s in 9e902e6.

Links

• Year 22 Number Royale (<50%) pointed at a (speed) file; the file is (both).
• Year 42 Important Email Organization (+50%) had doubled spaces in the URL, so it 404'd.

Rows that did not belong

Removed, along with their files, because they do not beat the +99% solution and so fail the folder rule:

• Year 42 Important Email Organization (+50%, size): 9 commands, same as the +99% entry, and slower.
• Year 44 Unique Fashion Party (+50%, speed): 17/1, identical scores to the +99% entry.
• Year 57 Neighborly Sweeper (+50%, size): 9 commands, same as the +99% entry, and slower.

Markers

Refreshed against the stat page's shortest/fastest known solution, which is what the markers compare with:

• Year 30 Fill the Floor (size): 5 is now the shortest known, so ✔ rather than ➕.
• Year 61 Lazy Pathways (size): the shortest known is now 7, so ❌ rather than ✔.
• Year 37 Dangerous Spreadsheeting (size): its speed of 32 was bold as if it were the best known, but the speed row
  is 10-11, so it is now plain.

One left alone: Year 38 Seek and Destroy 3 (speed) is ~11 ➕ and the fastest known is 11. If it only sometimes
hits 11 then ➖ would be the right marker — worth a second opinion from whoever recorded it.

Documentation

• The folder table now includes SolutionsLowPercent and states the rule that a less reliable solution is only listed
  if it is strictly better.
• Years 08, 27 and 45 are noted as having no OCD challenge, so nobody goes looking for them.
• The legend explains what Size, Speed, bold, ~ and the markers actually mean.
• New CONTRIBUTING.md covering how size and speed are measured, how solutions are ranked, how paste-only solutions are
  flagged and how credit works.
• "Creator" is now "Contributor", since the column records who provided the solution here rather than who found it
  first.
• Level name typos fixed ("Bugdet Bragade 2", "Soultions99+").

Paste-only solutions (#139)

Solutions that cannot be typed into the game's editor and have to be pasted in are now marked 📋 in the tables, with
the rule written down in CONTRIBUTING.md. Seeded with the cases identified in #139: Year 06 Little Exterminator 1 and
Year 19 Content Creators Bug Fix use a direction set on pickup/takefrom, and Year 15 Shred Lines (speed) uses
pickup n,ne. Anything else needs someone who can confirm which commands a level unlocks.

check_readme.py

New check, run on every pull request alongside check_names.py. It fails if:

• a link does not resolve, or points outside the section's folder;
• a solution file is not listed, or is listed twice;
• the Size column disagrees with the number of commands in the file;
• the bold column does not match the file's (size)/(speed)/(both) type;
• a +50% or <50% row does not beat the more reliable solution above it.

It reproduces the size the game reports (labels, endif/endwhile/endfor and comments are free; else and end
are not; a condition split over lines counts once), and running it against the tables before this change reported
exactly the rows fixed here. mypy is also added to the lint matrix, since tox already had the environment.

Workflows

• Both workflows now also run on pushes to master. Until now they only ran on pull requests, so anything committed
  straight to master was never checked.
• Least privilege contents: read token, and a concurrency group so superseded runs are cancelled.
• Dependabot moves from daily to weekly and groups all action updates into a single pull request instead of one each.

Templates

Issue forms for a better solution, a credit correction and a paste-only flag, so the details the policies ask for
actually get collected, plus a pull request checklist. The credit form asks for the dated public link that #43 said
was needed, and the paste-only form asks how the availability of the command was checked.