Add additional documentation to tokenizer and parser steps

[MrShwhale]

These commits complete documentation related to the tokenization step of ftml, and partially documents the parsing step. They also fixes the clippy and rustdoc warnings.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 76.77%. Comparing base (24bd66e) to head (97d71ea).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #13      +/-   ##
==========================================
+ Coverage   76.75%   76.77%   +0.01%     
==========================================
  Files         209      209              
  Lines        5516     5516              
==========================================
+ Hits         4234     4235       +1     
+ Misses       1282     1281       -1     

Flag	Coverage Δ
ftml	76.77% <ø> (+0.01%)	⬆️

Files	Coverage Δ
src/data/page_ref.rs	89.47% <ø> (ø)
src/parsing/mod.rs	90.14% <ø> (ø)
src/parsing/paragraph/stack.rs	86.53% <ø> (ø)
src/parsing/parser.rs	89.06% <ø> (ø)
src/parsing/rule/impls/block/blocks/later.rs	0.00% <ø> (ø)
src/parsing/rule/impls/block/blocks/mod.rs	100.00% <ø> (ø)
src/parsing/rule/mod.rs	66.66% <ø> (ø)
src/parsing/token/mod.rs	86.66% <ø> (ø)
src/render/html/element/mod.rs	95.71% <ø> (ø)
src/settings/interwiki.rs	92.59% <ø> (+3.70%)	⬆️
... and 6 more