Add deprecated messages for the next breaking release (`v0.7.0`)

[hyrodium]

The upcoming v0.7.0 version is going to have the following breaking changes.

• Remove normalize, normalizea, normalizeq (#69)
• Remove norm field (#60 #108)
• Remove rotation-related functions (#86)
• Remove Complex-Quaternion compatibility (#62)

This PR adds deprecated messages to these functions and their methods.

[codecov[bot]]

Codecov Report

Merging #110 (c14521d) into main (1bc31da) will decrease coverage by 1.32%. The diff coverage is 91.42%.

@@             Coverage Diff             @@
##              main     #110      +/-   ##
===========================================
- Coverage   100.00%   98.67%   -1.33%     
===========================================
  Files            1        1              
  Lines          199      227      +28     
===========================================
+ Hits           199      224      +25     
- Misses           0        3       +3     

Impacted Files	Coverage Δ
src/Quaternion.jl	98.67% <91.42%> (-1.33%)	:arrow_down:

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[hyrodium]

I'm not sure we really need additional tests for depwarns, but I will gladly add the tests if required.