fix: update broken python and blockly documentation links

[evemartin]

The following links have been fixed:

• the link in some Python Den levels' hints (i.e. Level 42's hint) to the full list of Python commands
• the "You can read more about Blockly here" link on the Rapid Router level selection page
• the "You can read more about Python here" link on the Rapid Router level selection page

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This change is 

[faucomte97]

Reviewed 2 of 2 files at r1, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @evemartin)